diff --git a/cmake/QtToolchainHelpers.cmake b/cmake/QtToolchainHelpers.cmake
index 1fc8cf6a892..5f3d2dc4d38 100644
--- a/cmake/QtToolchainHelpers.cmake
+++ b/cmake/QtToolchainHelpers.cmake
@@ -198,8 +198,8 @@ set(__qt_chainload_toolchain_file \"\${__qt_initially_configured_toolchain_file}
         # xcodebuild from the command line would try to build with the wrong architecture. Also
         # provide an opt-out option just in case.
         #
-        # For a multi-architecture build (so simulator_and_device) we don't set an explicit
-        # architecture and let Xcode and the developer handle it.
+        # For a multi-architecture build (so simulator_and_device) we set an explicit
+        # architecture for simulator only, via _qt_internal_set_ios_simulator_arch.
         #
         # When using the Ninja generator, specify the first architecture from QT_OSX_ARCHITECTURES
         # (even with a simulator_and_device Qt build). This ensures that the default configuration
diff --git a/src/corelib/Qt6CoreMacros.cmake b/src/corelib/Qt6CoreMacros.cmake
index 5ec1ed13593..75f41702491 100644
--- a/src/corelib/Qt6CoreMacros.cmake
+++ b/src/corelib/Qt6CoreMacros.cmake
@@ -1223,6 +1223,32 @@ function(_qt_internal_generate_ios_info_plist target)
     set_target_properties("${target}" PROPERTIES MACOSX_BUNDLE_INFO_PLIST "${info_plist_out}")
 endfunction()
 
+function(_qt_internal_set_ios_simulator_arch target)
+    if(CMAKE_XCODE_ATTRIBUTE_ARCHS
+        OR QT_NO_SET_XCODE_ARCHS)
+        return()
+    endif()
+
+    get_target_property(existing_archs
+        "${target}" XCODE_ATTRIBUTE_ARCHS)
+    if(NOT existing_archs MATCHES "-NOTFOUND")
+        return()
+    endif()
+
+    if(NOT x86_64 IN_LIST QT_OSX_ARCHITECTURES)
+        return()
+    endif()
+
+    if(CMAKE_OSX_ARCHITECTURES AND NOT x86_64 IN_LIST CMAKE_OSX_ARCHITECTURES)
+        return()
+    endif()
+
+    set_target_properties("${target}"
+        PROPERTIES
+        "XCODE_ATTRIBUTE_ARCHS[sdk=iphonesimulator*]"
+        "x86_64")
+endfunction()
+
 function(_qt_internal_finalize_apple_app target)
     # Shared between macOS and iOS apps
     _qt_internal_set_xcode_development_team_id("${target}")
@@ -1240,6 +1266,7 @@ function(_qt_internal_finalize_ios_app target)
     _qt_internal_set_xcode_bitcode_enablement("${target}")
     _qt_internal_handle_ios_launch_screen("${target}")
     _qt_internal_generate_ios_info_plist("${target}")
+    _qt_internal_set_ios_simulator_arch("${target}")
 endfunction()
 
 function(_qt_internal_finalize_macos_app target)