diff --git a/browser_patches/buildbots/buildbot-mac-11.0-arm64.sh b/browser_patches/buildbots/buildbot-mac-11.0-arm64.sh
index 18049982de..6b0aa1f0fb 100755
--- a/browser_patches/buildbots/buildbot-mac-11.0-arm64.sh
+++ b/browser_patches/buildbots/buildbot-mac-11.0-arm64.sh
@@ -63,3 +63,4 @@ fi
 
 git pull origin master
 ../checkout_build_archive_upload.sh webkit-mac-11.0-arm64 >/tmp/$(basename $0)--webkit-mac-11.0-arm64.log || true
+../checkout_build_archive_upload.sh firefox-mac-11.0-arm64 >/tmp/$(basename $0)--firefox-mac-11.0-arm64.log || true
diff --git a/browser_patches/checkout_build_archive_upload.sh b/browser_patches/checkout_build_archive_upload.sh
index 04c581c3d5..0672662631 100755
--- a/browser_patches/checkout_build_archive_upload.sh
+++ b/browser_patches/checkout_build_archive_upload.sh
@@ -100,6 +100,12 @@ elif [[ "$BUILD_FLAVOR" == "firefox-mac-10.14" ]]; then
   EXPECTED_HOST_OS="Darwin"
   EXPECTED_HOST_OS_VERSION="10.14"
   BUILD_BLOB_NAME="firefox-mac-10.14.zip"
+elif [[ "$BUILD_FLAVOR" == "firefox-mac-11.0-arm64" ]]; then
+  BROWSER_NAME="firefox"
+  EXPECTED_HOST_OS="Darwin"
+  EXPECTED_HOST_OS_VERSION="11.0"
+  EXPECTED_ARCH="arm64"
+  BUILD_BLOB_NAME="firefox-mac-11.0-arm64.zip"
 elif [[ "$BUILD_FLAVOR" == "firefox-win32" ]]; then
   BROWSER_NAME="firefox"
   EXPECTED_HOST_OS="MINGW"
diff --git a/browser_patches/firefox/build.sh b/browser_patches/firefox/build.sh
index 2c99182c1f..67c33aa8f4 100755
--- a/browser_patches/firefox/build.sh
+++ b/browser_patches/firefox/build.sh
@@ -23,18 +23,30 @@ fi
 
 
 if [[ "$(uname)" == "Darwin" ]]; then
-  # Firefox currently does not build on 10.15 out of the box - it requires SDK for 10.12.
-  # Make sure the SDK is out there.
-  if ! [[ -d $HOME/SDK-archive/MacOSX${MACOS_SDK_VERSION}.sdk ]]; then
-    echo "As of Dec 2020, Firefox does not build on Mac without ${MACOS_SDK_VERSION} SDK."
-    echo "Download XCode ${XCODE_VERSION_WITH_REQUIRED_SDK_VERSION} from https://developer.apple.com/download/more/ and"
-    echo "extract SDK to $HOME/SDK-archive/MacOSX${MACOS_SDK_VERSION}.sdk"
-    echo ""
-    echo "More info: https://firefox-source-docs.mozilla.org/setup/macos_build.html"
-    exit 1
+  if [[ $(uname -m) == "arm64" ]]; then
+    # Building on Apple Silicon requires XCode12.2 and does not require any extra SDKs.
+    if ! [[ -d "/Applications/Xcode12.2.app" ]]; then
+      echo "As of Jan 2021, building Firefox on Apple Silicon requires XCode 12.2"
+      echo "Make sure there's an /Applications/Xcode12.2.app"
+      echo "Download XCode from https://developer.apple.com/download/more/"
+      echo ""
+      exit 1
+    fi
+    export DEVELOPER_DIR=/Applications/Xcode12.2.app/Contents/Developer
   else
-    echo "-- configuting .mozconfig with ${MACOS_SDK_VERSION} SDK path"
-    echo "ac_add_options --with-macos-sdk=$HOME/SDK-archive/MacOSX${MACOS_SDK_VERSION}.sdk/" > .mozconfig
+    # Firefox currently does not build on 10.15 out of the box - it requires SDK for 10.12.
+    # Make sure the SDK is out there.
+    if ! [[ -d $HOME/SDK-archive/MacOSX${MACOS_SDK_VERSION}.sdk ]]; then
+      echo "As of Dec 2020, Firefox does not build on Mac without ${MACOS_SDK_VERSION} SDK."
+      echo "Download XCode ${XCODE_VERSION_WITH_REQUIRED_SDK_VERSION} from https://developer.apple.com/download/more/ and"
+      echo "extract SDK to $HOME/SDK-archive/MacOSX${MACOS_SDK_VERSION}.sdk"
+      echo ""
+      echo "More info: https://firefox-source-docs.mozilla.org/setup/macos_build.html"
+      exit 1
+    else
+      echo "-- configuting .mozconfig with ${MACOS_SDK_VERSION} SDK path"
+      echo "ac_add_options --with-macos-sdk=$HOME/SDK-archive/MacOSX${MACOS_SDK_VERSION}.sdk/" > .mozconfig
+    fi
   fi
   echo "-- building on Mac"
 elif [[ "$(uname)" == "Linux" ]]; then