diff --git a/chrome/content/zotero/import/importWizard.js b/chrome/content/zotero/import/importWizard.js
index 3f42467a3d..0b4ab7af4b 100644
--- a/chrome/content/zotero/import/importWizard.js
+++ b/chrome/content/zotero/import/importWizard.js
@@ -38,6 +38,7 @@ const { directAuth } = mendeleyAPIUtils;
 const Zotero_Import_Wizard = { // eslint-disable-line no-unused-vars
 	file: null,
 	folder: null,
+	isZotfileInstalled: false,
 	libraryID: null,
 	mendeleyAuth: null,
 	mendeleyCode: null,
@@ -69,6 +70,9 @@ const Zotero_Import_Wizard = { // eslint-disable-line no-unused-vars
 			this.mendeleyHasPreviouslyImported = !!(await Zotero.DB.valueQueryAsync(relSQL, predicateID));
 		}
 
+		const extensions = await Zotero.getInstalledExtensions();
+		this.isZotfileInstalled = !!extensions.find(extName => extName.match(/^ZotFile((?!disabled).)*$/));
+
 		this.wizard = document.getElementById('import-wizard');
 		this.wizard.getPageById('page-start')
 			.addEventListener('pageadvanced', this.onImportSourceAdvance.bind(this));
@@ -272,6 +276,13 @@ const Zotero_Import_Wizard = { // eslint-disable-line no-unused-vars
 				case 'mendeleyOnline':
 					this.file = null;
 					this.folder = null;
+					if (this.isZotfileInstalled) {
+						this.skipToDonePage(
+							'general-error',
+							['import-online-blocked-by-plugin', { plugin: 'ZotFile' }]
+						);
+						return;
+					}
 					this.wizard.goTo('page-mendeley-online-intro');
 					this.wizard.canRewind = true;
 					break;
diff --git a/chrome/locale/en-US/zotero/zotero.ftl b/chrome/locale/en-US/zotero/zotero.ftl
index 32da2f0b54..2316d11b62 100644
--- a/chrome/locale/en-US/zotero/zotero.ftl
+++ b/chrome/locale/en-US/zotero/zotero.ftl
@@ -60,6 +60,7 @@ import-online-intro=In the next step you will be asked to log in to { $targetApp
 import-online-intro2={ -app-name } will never see or store your { $targetApp } password.
 import-online-form-intro = Please enter your credentials to log in to { $targetAppOnline }. This is necessary to import your { $targetApp } library into { -app-name }.
 import-online-wrong-credentials = Login to { $targetApp } failed. Please re-enter credentials and try again.
+import-online-blocked-by-plugin = The import cannot continue with { $plugin } installed. Please disable this plugin and try again.
 
 report-error =
     .label = Report Error…