diff --git a/src/api/providers/__tests__/bedrock-custom-region.spec.ts b/src/api/providers/__tests__/bedrock-custom-region.spec.ts
new file mode 100644
index 0000000000..522d01c1b2
--- /dev/null
+++ b/src/api/providers/__tests__/bedrock-custom-region.spec.ts
@@ -0,0 +1,107 @@
+import { describe, it, expect, vi, beforeEach } from "vitest"
+import { AwsBedrockHandler } from "../bedrock"
+import { BedrockRuntimeClient } from "@aws-sdk/client-bedrock-runtime"
+
+// Mock the AWS SDK
+vi.mock("@aws-sdk/client-bedrock-runtime", () => ({
+	BedrockRuntimeClient: vi.fn().mockImplementation((config) => ({
+		config,
+		send: vi.fn(),
+	})),
+	ConverseCommand: vi.fn(),
+	ConverseStreamCommand: vi.fn(),
+}))
+
+describe("AwsBedrockHandler - Custom Region Support", () => {
+	beforeEach(() => {
+		vi.clearAllMocks()
+	})
+
+	it("should use custom region when awsRegion is 'custom' and awsCustomRegion is provided", () => {
+		const handler = new AwsBedrockHandler({
+			apiProvider: "bedrock",
+			apiModelId: "anthropic.claude-3-sonnet-20240229-v1:0",
+			awsAccessKey: "test-access-key",
+			awsSecretKey: "test-secret-key",
+			awsRegion: "custom",
+			awsCustomRegion: "us-west-3",
+		})
+
+		// Get the mock instance to check the config
+		const mockClientInstance = vi.mocked(BedrockRuntimeClient).mock.results[0]?.value
+		expect(mockClientInstance.config.region).toBe("us-west-3")
+	})
+
+	it("should use standard region when awsRegion is not 'custom'", () => {
+		const handler = new AwsBedrockHandler({
+			apiProvider: "bedrock",
+			apiModelId: "anthropic.claude-3-sonnet-20240229-v1:0",
+			awsAccessKey: "test-access-key",
+			awsSecretKey: "test-secret-key",
+			awsRegion: "us-east-1",
+			awsCustomRegion: "us-west-3", // This should be ignored
+		})
+
+		// Get the mock instance to check the config
+		const mockClientInstance = vi.mocked(BedrockRuntimeClient).mock.results[0]?.value
+		expect(mockClientInstance.config.region).toBe("us-east-1")
+	})
+
+	it("should use awsRegion when awsCustomRegion is not provided", () => {
+		const handler = new AwsBedrockHandler({
+			apiProvider: "bedrock",
+			apiModelId: "anthropic.claude-3-sonnet-20240229-v1:0",
+			awsAccessKey: "test-access-key",
+			awsSecretKey: "test-secret-key",
+			awsRegion: "custom",
+			// awsCustomRegion is not provided
+		})
+
+		// Get the mock instance to check the config
+		const mockClientInstance = vi.mocked(BedrockRuntimeClient).mock.results[0]?.value
+		expect(mockClientInstance.config.region).toBe("custom")
+	})
+
+	it("should use custom region for cross-region inference prefix calculation", () => {
+		const handler = new AwsBedrockHandler({
+			apiProvider: "bedrock",
+			apiModelId: "anthropic.claude-3-sonnet-20240229-v1:0",
+			awsAccessKey: "test-access-key",
+			awsSecretKey: "test-secret-key",
+			awsRegion: "custom",
+			awsCustomRegion: "us-west-3",
+			awsUseCrossRegionInference: true,
+		})
+
+		const model = handler.getModel()
+		// Should have the us. prefix for us-west-3
+		expect(model.id).toContain("us.")
+	})
+
+	it("should handle custom regions with different prefixes for cross-region inference", () => {
+		const testCases = [
+			{ customRegion: "eu-central-3", expectedPrefix: "eu." },
+			{ customRegion: "ap-southeast-4", expectedPrefix: "apac." },
+			{ customRegion: "ca-west-1", expectedPrefix: "ca." },
+			{ customRegion: "sa-east-2", expectedPrefix: "sa." },
+			{ customRegion: "us-gov-west-2", expectedPrefix: "ug." },
+		]
+
+		for (const { customRegion, expectedPrefix } of testCases) {
+			vi.clearAllMocks()
+
+			const handler = new AwsBedrockHandler({
+				apiProvider: "bedrock",
+				apiModelId: "anthropic.claude-3-sonnet-20240229-v1:0",
+				awsAccessKey: "test-access-key",
+				awsSecretKey: "test-secret-key",
+				awsRegion: "custom",
+				awsCustomRegion: customRegion,
+				awsUseCrossRegionInference: true,
+			})
+
+			const model = handler.getModel()
+			expect(model.id).toContain(expectedPrefix)
+		}
+	})
+})
diff --git a/src/api/providers/bedrock.ts b/src/api/providers/bedrock.ts
index a25fea5200..3ace00f525 100644
--- a/src/api/providers/bedrock.ts
+++ b/src/api/providers/bedrock.ts
@@ -169,7 +169,11 @@ export class AwsBedrockHandler extends BaseProvider implements SingleCompletionH
 	constructor(options: ProviderSettings) {
 		super()
 		this.options = options
-		let region = this.options.awsRegion
+		// Use custom region if awsRegion is "custom"
+		let region =
+			this.options.awsRegion === "custom" && this.options.awsCustomRegion
+				? this.options.awsCustomRegion
+				: this.options.awsRegion
 
 		// process the various user input options, be opinionated about the intent of the options
 		// and determine the model to use during inference and for cost calculations
@@ -216,7 +220,7 @@ export class AwsBedrockHandler extends BaseProvider implements SingleCompletionH
 		this.costModelConfig = this.getModel()
 
 		const clientConfig: BedrockRuntimeClientConfig = {
-			region: this.options.awsRegion,
+			region: region, // Use the resolved region (either standard or custom)
 			// Add the endpoint configuration when specified and enabled
 			...(this.options.awsBedrockEndpoint &&
 				this.options.awsBedrockEndpointEnabled && { endpoint: this.options.awsBedrockEndpoint }),
@@ -943,10 +947,18 @@ export class AwsBedrockHandler extends BaseProvider implements SingleCompletionH
 			modelConfig = this.getModelById(this.options.apiModelId as string)
 
 			// Add cross-region inference prefix if enabled
-			if (this.options.awsUseCrossRegionInference && this.options.awsRegion) {
-				const prefix = AwsBedrockHandler.getPrefixForRegion(this.options.awsRegion)
-				if (prefix) {
-					modelConfig.id = `${prefix}${modelConfig.id}`
+			if (this.options.awsUseCrossRegionInference) {
+				// Use custom region if awsRegion is "custom"
+				const regionToUse =
+					this.options.awsRegion === "custom" && this.options.awsCustomRegion
+						? this.options.awsCustomRegion
+						: this.options.awsRegion
+
+				if (regionToUse) {
+					const prefix = AwsBedrockHandler.getPrefixForRegion(regionToUse)
+					if (prefix) {
+						modelConfig.id = `${prefix}${modelConfig.id}`
+					}
 				}
 			}
 		}
diff --git a/webview-ui/src/components/settings/providers/Bedrock.tsx b/webview-ui/src/components/settings/providers/Bedrock.tsx
index 86bb225111..1b51ea594e 100644
--- a/webview-ui/src/components/settings/providers/Bedrock.tsx
+++ b/webview-ui/src/components/settings/providers/Bedrock.tsx
@@ -9,6 +9,9 @@ import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue, Standard
 
 import { inputEventTransform, noTransform } from "../transforms"
 
+// AWS region format validation regex
+const AWS_REGION_REGEX = /^[a-z]{2,}-[a-z]+-\d+$/
+
 type BedrockProps = {
 	apiConfiguration: ProviderSettings
 	setApiConfigurationField: (field: keyof ProviderSettings, value: ProviderSettings[keyof ProviderSettings]) => void
@@ -19,6 +22,7 @@ export const Bedrock = ({ apiConfiguration, setApiConfigurationField, selectedMo
 	const { t } = useAppTranslation()
 	const [awsEndpointSelected, setAwsEndpointSelected] = useState(!!apiConfiguration?.awsBedrockEndpointEnabled)
 	const [customRegionSelected, setCustomRegionSelected] = useState(apiConfiguration?.awsRegion === "custom")
+	const [customRegionError, setCustomRegionError] = useState<string | null>(null)
 
 	// Update the endpoint enabled state when the configuration changes
 	useEffect(() => {
@@ -41,6 +45,34 @@ export const Bedrock = ({ apiConfiguration, setApiConfigurationField, selectedMo
 		[setApiConfigurationField],
 	)
 
+	// Validate custom region format
+	const validateCustomRegion = useCallback(
+		(value: string) => {
+			if (!value && customRegionSelected) {
+				setCustomRegionError(t("settings:providers.awsCustomRegion.validation.required"))
+				return false
+			}
+			if (value && !AWS_REGION_REGEX.test(value)) {
+				setCustomRegionError(t("settings:providers.awsCustomRegion.validation.format"))
+				return false
+			}
+			setCustomRegionError(null)
+			return true
+		},
+		[customRegionSelected, t],
+	)
+
+	// Handle custom region input change with validation
+	const handleCustomRegionChange = useCallback(
+		(event: Event | React.FormEvent<HTMLElement>) => {
+			const target = event.target as HTMLInputElement
+			const value = target.value
+			validateCustomRegion(value)
+			setApiConfigurationField("awsCustomRegion", value)
+		},
+		[setApiConfigurationField, validateCustomRegion],
+	)
+
 	return (
 		<>
 			<VSCodeRadioGroup
@@ -98,9 +130,13 @@ export const Bedrock = ({ apiConfiguration, setApiConfigurationField, selectedMo
 					onValueChange={(value) => {
 						setApiConfigurationField("awsRegion", value)
 						setCustomRegionSelected(value === "custom")
-						// Clear custom region when switching to a standard region
-						if (value !== "custom") {
-							setApiConfigurationField("awsCustomRegion", "")
+						// Don't clear custom region when switching away - preserve the value
+						if (value === "custom" && apiConfiguration?.awsCustomRegion) {
+							// Validate the existing custom region value
+							validateCustomRegion(apiConfiguration.awsCustomRegion)
+						} else {
+							// Clear validation error when not using custom region
+							setCustomRegionError(null)
 						}
 					}}>
 					<SelectTrigger className="w-full">
@@ -120,10 +156,14 @@ export const Bedrock = ({ apiConfiguration, setApiConfigurationField, selectedMo
 					<VSCodeTextField
 						value={apiConfiguration?.awsCustomRegion || ""}
 						style={{ width: "100%", marginTop: 3, marginBottom: 5 }}
-						onInput={handleInputChange("awsCustomRegion")}
-						placeholder={t("settings:placeholders.customRegion")}
+						onInput={handleCustomRegionChange}
+						placeholder={t("settings:providers.awsCustomRegion.placeholder")}
 						data-testid="custom-region-input"
+						className={customRegionError ? "error" : ""}
 					/>
+					{customRegionError && (
+						<div className="text-sm text-vscode-errorForeground ml-6 mt-1 mb-2">{customRegionError}</div>
+					)}
 					<div className="text-sm text-vscode-descriptionForeground ml-6 mt-1 mb-3">
 						{t("settings:providers.awsCustomRegion.examples")}
 						<div className="ml-2">• us-west-3</div>
diff --git a/webview-ui/src/components/settings/providers/__tests__/Bedrock.spec.tsx b/webview-ui/src/components/settings/providers/__tests__/Bedrock.spec.tsx
index 80c1c4fd90..a2f6774563 100644
--- a/webview-ui/src/components/settings/providers/__tests__/Bedrock.spec.tsx
+++ b/webview-ui/src/components/settings/providers/__tests__/Bedrock.spec.tsx
@@ -61,11 +61,18 @@ vi.mock("@src/i18n/TranslationContext", () => ({
 
 // Mock the UI components
 vi.mock("@src/components/ui", () => ({
-	Select: ({ children }: any) => <div>{children}</div>,
+	Select: ({ children, onValueChange }: any) => {
+		// Store the onValueChange callback on the window for testing
+		if (typeof window !== "undefined") {
+			;(window as any).__selectOnValueChange = onValueChange
+		}
+		return <div data-testid="select-component">{children}</div>
+	},
 	SelectContent: ({ children }: any) => <div>{children}</div>,
 	SelectItem: () => <div>Item</div>,
-	SelectTrigger: ({ children }: any) => <div>{children}</div>,
+	SelectTrigger: ({ children }: any) => <div role="combobox">{children}</div>,
 	SelectValue: () => <div>Value</div>,
+	StandardTooltip: ({ children }: any) => <div>{children}</div>,
 }))
 
 // Mock the constants
@@ -636,4 +643,196 @@ describe("Bedrock Component", () => {
 			expect(screen.getByText("settings:providers.awsCustomRegion.examples")).toBeInTheDocument()
 		})
 	})
+
+	// Test Scenario 7: Custom Region Validation Tests
+	describe("Custom Region Validation", () => {
+		it("should show validation error when custom region is empty", () => {
+			const apiConfiguration: Partial<ProviderSettings> = {
+				awsRegion: "custom",
+				awsCustomRegion: "",
+				awsUseProfile: true,
+			}
+
+			render(
+				<Bedrock
+					apiConfiguration={apiConfiguration as ProviderSettings}
+					setApiConfigurationField={mockSetApiConfigurationField}
+				/>,
+			)
+
+			// The custom region input should be visible
+			const customRegionInput = screen.getByTestId("custom-region-input")
+			expect(customRegionInput).toBeInTheDocument()
+
+			// Trigger validation by changing input
+			fireEvent.change(customRegionInput, { target: { value: "" } })
+
+			// Should show required validation error
+			expect(screen.getByText("settings:providers.awsCustomRegion.validation.required")).toBeInTheDocument()
+		})
+
+		it("should show validation error for invalid region format", () => {
+			const apiConfiguration: Partial<ProviderSettings> = {
+				awsRegion: "custom",
+				awsCustomRegion: "",
+				awsUseProfile: true,
+			}
+
+			render(
+				<Bedrock
+					apiConfiguration={apiConfiguration as ProviderSettings}
+					setApiConfigurationField={mockSetApiConfigurationField}
+				/>,
+			)
+
+			const customRegionInput = screen.getByTestId("custom-region-input")
+
+			// Test various invalid formats
+			const invalidRegions = [
+				"invalid-region",
+				"us-west",
+				"us-3",
+				"uswest3",
+				"US-WEST-3",
+				"us-west-three",
+				"123-west-3",
+			]
+
+			for (const invalidRegion of invalidRegions) {
+				fireEvent.change(customRegionInput, { target: { value: invalidRegion } })
+
+				// Should show format validation error
+				expect(screen.getByText("settings:providers.awsCustomRegion.validation.format")).toBeInTheDocument()
+			}
+		})
+
+		it("should accept valid region formats", () => {
+			const apiConfiguration: Partial<ProviderSettings> = {
+				awsRegion: "custom",
+				awsCustomRegion: "",
+				awsUseProfile: true,
+			}
+
+			render(
+				<Bedrock
+					apiConfiguration={apiConfiguration as ProviderSettings}
+					setApiConfigurationField={mockSetApiConfigurationField}
+				/>,
+			)
+
+			const customRegionInput = screen.getByTestId("custom-region-input")
+
+			// Test various valid formats
+			const validRegions = [
+				"us-west-3",
+				"eu-central-2",
+				"ap-southeast-4",
+				"sa-east-2",
+				"ca-west-1",
+				"me-south-2",
+				"af-south-1",
+			]
+
+			for (const validRegion of validRegions) {
+				fireEvent.change(customRegionInput, { target: { value: validRegion } })
+
+				// Should update the field
+				expect(mockSetApiConfigurationField).toHaveBeenCalledWith("awsCustomRegion", validRegion)
+
+				// Should not show any error
+				expect(
+					screen.queryByText("settings:providers.awsCustomRegion.validation.format"),
+				).not.toBeInTheDocument()
+				expect(
+					screen.queryByText("settings:providers.awsCustomRegion.validation.required"),
+				).not.toBeInTheDocument()
+			}
+		})
+
+		it("should preserve custom region value when switching between regions", () => {
+			const apiConfiguration: Partial<ProviderSettings> = {
+				awsRegion: "custom",
+				awsCustomRegion: "us-west-3",
+				awsUseProfile: true,
+			}
+
+			const { rerender } = render(
+				<Bedrock
+					apiConfiguration={apiConfiguration as ProviderSettings}
+					setApiConfigurationField={mockSetApiConfigurationField}
+				/>,
+			)
+
+			// Custom region input should be visible with the value
+			let customRegionInput = screen.getByTestId("custom-region-input") as HTMLInputElement
+			expect(customRegionInput.value).toBe("us-west-3")
+
+			// Switch to a standard region by calling the onValueChange directly
+			if ((window as any).__selectOnValueChange) {
+				;(window as any).__selectOnValueChange("us-east-1")
+			}
+
+			// Update the configuration
+			apiConfiguration.awsRegion = "us-east-1"
+			rerender(
+				<Bedrock
+					apiConfiguration={apiConfiguration as ProviderSettings}
+					setApiConfigurationField={mockSetApiConfigurationField}
+				/>,
+			)
+
+			// Custom region input should be hidden
+			expect(screen.queryByTestId("custom-region-input")).not.toBeInTheDocument()
+
+			// Switch back to custom region
+			if ((window as any).__selectOnValueChange) {
+				;(window as any).__selectOnValueChange("custom")
+			}
+
+			// Update the configuration
+			apiConfiguration.awsRegion = "custom"
+			rerender(
+				<Bedrock
+					apiConfiguration={apiConfiguration as ProviderSettings}
+					setApiConfigurationField={mockSetApiConfigurationField}
+				/>,
+			)
+
+			// Custom region input should be visible again with the preserved value
+			customRegionInput = screen.getByTestId("custom-region-input") as HTMLInputElement
+			expect(customRegionInput.value).toBe("us-west-3")
+		})
+
+		it("should validate existing custom region when switching back to custom", () => {
+			const apiConfiguration: Partial<ProviderSettings> = {
+				awsRegion: "us-east-1",
+				awsCustomRegion: "invalid-region", // Invalid format
+				awsUseProfile: true,
+			}
+
+			const { rerender } = render(
+				<Bedrock
+					apiConfiguration={apiConfiguration as ProviderSettings}
+					setApiConfigurationField={mockSetApiConfigurationField}
+				/>,
+			)
+
+			// Switch to custom region
+			if ((window as any).__selectOnValueChange) {
+				;(window as any).__selectOnValueChange("custom")
+			}
+
+			// Update the configuration
+			apiConfiguration.awsRegion = "custom"
+			rerender(
+				<Bedrock
+					apiConfiguration={apiConfiguration as ProviderSettings}
+					setApiConfigurationField={mockSetApiConfigurationField}
+				/>,
+			)
+
+			// Should show validation error for the existing invalid value
+			expect(screen.getByText("settings:providers.awsCustomRegion.validation.format")).toBeInTheDocument()
+		})
+	})
 })
diff --git a/webview-ui/src/i18n/locales/en/settings.json b/webview-ui/src/i18n/locales/en/settings.json
index 728e856502..29b8ea497b 100644
--- a/webview-ui/src/i18n/locales/en/settings.json
+++ b/webview-ui/src/i18n/locales/en/settings.json
@@ -273,6 +273,14 @@
 		"awsSessionToken": "AWS Session Token",
 		"awsRegion": "AWS Region",
 		"awsCrossRegion": "Use cross-region inference",
+		"awsCustomRegion": {
+			"placeholder": "Enter custom region (e.g., us-west-3)",
+			"examples": "Examples of new or custom regions:",
+			"validation": {
+				"required": "Custom region is required when 'Custom region...' is selected",
+				"format": "Region must be in format: region-direction-number (e.g., us-west-3, eu-central-2)"
+			}
+		},
 		"awsBedrockVpc": {
 			"useCustomVpcEndpoint": "Use custom VPC endpoint",
 			"vpcEndpointUrlPlaceholder": "Enter VPC Endpoint URL (optional)",
@@ -686,6 +694,7 @@
 		"keyFilePath": "Enter Key File Path...",
 		"projectId": "Enter Project ID...",
 		"customArn": "Enter ARN (e.g. arn:aws:bedrock:us-east-1:123456789012:foundation-model/my-model)",
+		"customRegion": "Enter custom region (e.g., us-west-3)",
 		"baseUrl": "Enter base URL...",
 		"modelId": {
 			"lmStudio": "e.g. meta-llama-3.1-8b-instruct",