diff --git a/platform/android/export/export_plugin.cpp b/platform/android/export/export_plugin.cpp
index 5d31c4911c5b..c94119e13d52 100644
--- a/platform/android/export/export_plugin.cpp
+++ b/platform/android/export/export_plugin.cpp
@@ -49,7 +49,7 @@
 #include "editor/editor_settings.h"
 #include "main/splash.gen.h"
 
-#include "modules/modules_enabled.gen.h" // For svg.
+#include "modules/modules_enabled.gen.h" // For mono and svg.
 #ifdef MODULE_SVG_ENABLED
 #include "modules/svg/image_loader_svg.h"
 #endif
@@ -2232,6 +2232,14 @@ bool EditorExportPlatformAndroid::has_valid_export_configuration(const Ref<Edito
 	bool valid = false;
 	const bool gradle_build_enabled = p_preset->get("gradle_build/use_gradle_build");
 
+#ifdef MODULE_MONO_ENABLED
+	err += TTR("Exporting to Android is currently not supported in Godot 4 when using C#/.NET. Use Godot 3 to target Android with C#/Mono instead.") + "\n";
+	err += TTR("If this project does not use C#, use a non-C# editor build to export the project.") + "\n";
+	// Don't check for additional errors, as this particular error cannot be resolved.
+	r_error = err;
+	return false;
+#endif
+
 	// Look for export templates (first official, and if defined custom templates).
 
 	if (!gradle_build_enabled) {
diff --git a/platform/ios/export/export_plugin.cpp b/platform/ios/export/export_plugin.cpp
index 1b9b02d0e07d..edc850e74fd5 100644
--- a/platform/ios/export/export_plugin.cpp
+++ b/platform/ios/export/export_plugin.cpp
@@ -37,7 +37,7 @@
 #include "editor/editor_scale.h"
 #include "editor/export/editor_export.h"
 
-#include "modules/modules_enabled.gen.h" // For svg.
+#include "modules/modules_enabled.gen.h" // For mono and svg.
 #ifdef MODULE_SVG_ENABLED
 #include "modules/svg/image_loader_svg.h"
 #endif
@@ -1903,6 +1903,14 @@ bool EditorExportPlatformIOS::has_valid_export_configuration(const Ref<EditorExp
 	String err;
 	bool valid = false;
 
+#ifdef MODULE_MONO_ENABLED
+	err += TTR("Exporting to iOS is currently not supported in Godot 4 when using C#/.NET. Use Godot 3 to target iOS with C#/Mono instead.") + "\n";
+	err += TTR("If this project does not use C#, use a non-C# editor build to export the project.") + "\n";
+	// Don't check for additional errors, as this particular error cannot be resolved.
+	r_error = err;
+	return false;
+#endif
+
 	// Look for export templates (first official, and if defined custom templates).
 
 	bool dvalid = exists_export_template("ios.zip", &err);
diff --git a/platform/web/export/export_plugin.cpp b/platform/web/export/export_plugin.cpp
index 0bc3b92f090a..38d7ed7fb6c1 100644
--- a/platform/web/export/export_plugin.cpp
+++ b/platform/web/export/export_plugin.cpp
@@ -38,7 +38,7 @@
 #include "editor/editor_settings.h"
 #include "editor/export/editor_export.h"
 
-#include "modules/modules_enabled.gen.h" // For svg.
+#include "modules/modules_enabled.gen.h" // For mono and svg.
 #ifdef MODULE_SVG_ENABLED
 #include "modules/svg/image_loader_svg.h"
 #endif
@@ -363,6 +363,14 @@ bool EditorExportPlatformWeb::has_valid_export_configuration(const Ref<EditorExp
 	bool valid = false;
 	bool extensions = (bool)p_preset->get("variant/extensions_support");
 
+#ifdef MODULE_MONO_ENABLED
+	err += TTR("Exporting to Web is currently not supported in Godot 4 when using C#/.NET. Use Godot 3 to target Web with C#/Mono instead.") + "\n";
+	err += TTR("If this project does not use C#, use a non-C# editor build to export the project.") + "\n";
+	// Don't check for additional errors, as this particular error cannot be resolved.
+	r_error = err;
+	return false;
+#endif
+
 	// Look for export templates (first official, and if defined custom templates).
 	bool dvalid = exists_export_template(_get_template_name(extensions, true), &err);
 	bool rvalid = exists_export_template(_get_template_name(extensions, false), &err);