diff --git a/.github/workflows/downstream_protobuf_compatibility_check_nightly.yaml b/.github/workflows/downstream_protobuf_compatibility_check_nightly.yaml
index a186a8527b..df107ac4a8 100644
--- a/.github/workflows/downstream_protobuf_compatibility_check_nightly.yaml
+++ b/.github/workflows/downstream_protobuf_compatibility_check_nightly.yaml
@@ -43,12 +43,17 @@ jobs:
         # which values to use and would resolve to ''.
         protobuf-version: ${{ fromJSON(format('[{0}]', inputs.protobuf_runtime_versions || '"3.25.5","4.28.3"')) }}
     steps:
-      - uses: actions/checkout@v4
+      - name: Checkout sdk-platform-java repo
+        uses: actions/checkout@v4
       - uses: actions/setup-java@v4
         with:
-          java-version: 17
+          # Use Java 11 for this as Linkage Checker is only compatible with Java 11 or below
+          java-version: 11
           distribution: temurin
       - name: Print Protobuf-Java testing version
         run: echo "Testing with Protobuf-Java v${{ matrix.protobuf-version }}"
       - name: Perform downstream source compatibility testing
-        run: REPOS_UNDER_TEST="${{ matrix.repo }}" PROTOBUF_RUNTIME_VERSION="${{ matrix.protobuf-version}}" ./.kokoro/nightly/downstream-protobuf-source-compatibility.sh
+        run: REPOS_UNDER_TEST="${{ matrix.repo }}" PROTOBUF_RUNTIME_VERSION="${{ matrix.protobuf-version }}" ./.kokoro/nightly/downstream-protobuf-source-compatibility.sh
+      - name: Perform downstream binary compatibility testing
+        run: REPOS_UNDER_TEST="${{ matrix.repo }}" PROTOBUF_RUNTIME_VERSION="${{ matrix.protobuf-version }}" ./.kokoro/nightly/downstream-protobuf-binary-compatibility.sh
+
diff --git a/.kokoro/nightly/common.sh b/.kokoro/nightly/common.sh
new file mode 100644
index 0000000000..ee30ec3c74
--- /dev/null
+++ b/.kokoro/nightly/common.sh
@@ -0,0 +1,31 @@
+#!/bin/bash
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Checks that the protobuf compatibility scripts provide non-empty input
+function validate_protobuf_compatibility_script_inputs {
+  # Comma-delimited list of repos to test
+  if [ -z "${REPOS_UNDER_TEST}" ]; then
+    echo "REPOS_UNDER_TEST Env Var must be set. This script expects a"
+    echo "comma-delimited list: i.e REPOS_UNDER_TEST=\"java-bigtable,java-bigquery\""
+    exit 1
+  fi
+
+  # A single version of Protobuf-Java runtime to test
+  if [ -z "${PROTOBUF_RUNTIME_VERSION}" ]; then
+    echo "PROTOBUF_RUNTIME_VERSION Env Var must be set. This script expects a single "
+    echo "Protobuf-Java runtime version i.e. PROTOBUF_RUNTIME_VERSION=\"4.28.3\""
+    exit 1
+  fi
+}
\ No newline at end of file
diff --git a/.kokoro/nightly/downstream-protobuf-binary-compatibility.sh b/.kokoro/nightly/downstream-protobuf-binary-compatibility.sh
new file mode 100755
index 0000000000..46dd4e967c
--- /dev/null
+++ b/.kokoro/nightly/downstream-protobuf-binary-compatibility.sh
@@ -0,0 +1,96 @@
+#!/bin/bash
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -eo pipefail
+
+scriptDir=$(realpath "$(dirname "${BASH_SOURCE[0]}")")
+source "${scriptDir}/common.sh"
+
+validate_protobuf_compatibility_script_inputs
+
+# Declare a map of downstream handwritten libraries and the relevant artifacts to test. The map stores a
+# K/V pairing of (Key: repo name, Value: comma separate list of Group ID:Artifact ID pairings). Note: The
+# value list doesn't hold the version and this needs to be parsed from the repo's versions.txt file
+declare -A repo_linkage_checker_arguments
+repo_linkage_checker_arguments["google-cloud-java"]="io.grafeas:grafeas,com.google.cloud:google-cloud-vertexai,com.google.cloud:google-cloud-resourcemanager,com.google.cloud:google-cloud-translate,com.google.api.grpc:grpc-google-cloud-vertexai-v1,com.google.api.grpc:grpc-google-cloud-vertexai-v1beta1,com.google.api.grpc:grpc-google-cloud-resourcemanager-v3,com.google.api.grpc:grpc-google-cloud-translate-v3,com.google.api.grpc:grpc-google-cloud-translate-v3beta1"
+repo_linkage_checker_arguments["java-bigtable"]="com.google.cloud:google-cloud-bigtable,com.google.api.grpc:grpc-google-cloud-bigtable-admin-v2,com.google.api.grpc:grpc-google-cloud-bigtable-v2"
+repo_linkage_checker_arguments["java-bigquery"]="com.google.cloud:google-cloud-bigquery"
+repo_linkage_checker_arguments["java-bigquerystorage"]="com.google.cloud:google-cloud-bigquerystorage,com.google.api.grpc:grpc-google-cloud-bigquerystorage-v1beta1,com.google.api.grpc:grpc-google-cloud-bigquerystorage-v1beta2,com.google.api.grpc:grpc-google-cloud-bigquerystorage-v1,com.google.api.grpc:grpc-google-cloud-bigquerystorage-v1alpha"
+repo_linkage_checker_arguments["java-datastore"]="com.google.cloud:google-cloud-datastore,com.google.cloud.datastre:datastore-v1-proto-client,com.google.api.grpc:grpc-google-cloud-datastore-admin-v1"
+repo_linkage_checker_arguments["java-firestore"]="com.google.cloud:google-cloud-firestore,com.google.cloud:google-cloud-firestore-admin,com.google.api.grpc:grpc-google-cloud-firestore-admin-v1,com.google.api.grpc:grpc-google-cloud-firestore-v1"
+repo_linkage_checker_arguments["java-logging"]="com.google.cloud:google-cloud-logging,com.google.api.grpc:grpc-google-cloud-logging-v2"
+repo_linkage_checker_arguments["java-logging-logback"]="com.google.cloud:google-cloud-logging-logback"
+repo_linkage_checker_arguments["java-pubsub"]="com.google.cloud:google-cloud-pubsub,com.google.api.grpc:grpc-google-cloud-pubsub-v1"
+repo_linkage_checker_arguments["java-pubsublite"]="com.google.cloud:google-cloud-pubsublite,com.google.api.grpc:grpc-google-cloud-pubsublite-v1"
+repo_linkage_checker_arguments["java-spanner-jdbc"]="com.google.cloud:google-cloud-spanner-jdbc"
+repo_linkage_checker_arguments["java-spanner"]="com.google.cloud:google-cloud-spanner,com.google.cloud:google-cloud-spanner-executor,com.google.api.grpc:grpc-google-cloud-spanner-v1,com.google.api.grpc:grpc-google-cloud-spanner-admin-instance-v1,com.google.api.grpc:grpc-google-cloud-spanner-admin-database-v1,com.google.api.grpc:grpc-google-cloud-spanner-executor-v1"
+repo_linkage_checker_arguments["java-storage"]="com.google.cloud:google-cloud-storage,com.google.api.grpc:gapic-google-cloud-storage-v2,com.google.api.grpc:grpc-google-cloud-storage-v2,com.google.cloud:google-cloud-storage-control,com.google.api.grpc:grpc-google-cloud-storage-control-v2"
+repo_linkage_checker_arguments["java-storage-nio"]="com.google.cloud:google-cloud-nio"
+
+# This function requires access to the versions.txt to retrieve the versions for the artifacts
+# It will try to match the artifact_id in the versions.txt file and attach it to form the GAV
+# The GAV list is required by Linkage Checker as program arguments
+function build_program_arguments() {
+  artifact_list="${repo_linkage_checker_arguments[$1]}"
+
+  for artifact in ${artifact_list//,/ }; do # Split on comma
+    artifact_id=$(echo "${artifact}" | cut -d ':' -f2)
+
+    # The grep query tries to match `{artifact_id}:{released_version}:{current_version}`.
+    # The artifact_id must be exact otherwise multiple entries may match
+    version=$(cat "versions.txt" | grep -E "^${artifact_id}:.*:.*$" | cut -d ':' -f3)
+    repo_gav_coordinate="${artifact}:${version}"
+
+    # The first entry added is not separated with a comma. Avoids generating `,{ARTIFACT_LIST}`
+    if [ -z "${linkage_checker_arguments}" ]; then
+      linkage_checker_arguments="${repo_gav_coordinate}"
+    else
+      linkage_checker_arguments="${linkage_checker_arguments},${repo_gav_coordinate}"
+    fi
+  done
+}
+
+# cloud-opensource-java contains the Linkage Checker tool
+git clone https://github.com/GoogleCloudPlatform/cloud-opensource-java.git
+pushd cloud-opensource-java
+mvn -B -ntp clean compile -T 1C
+# Linkage Checker tool resides in the /dependencies subfolder
+pushd dependencies
+
+# REPOS_UNDER_TEST Env Var accepts a comma separated list of googleapis repos to test. For Github CI,
+# this will be a single repo as Github will build a matrix of repos with each repo being tested in parallel.
+# For local invocation, you can pass a list of repos to test multiple repos together.
+for repo in ${REPOS_UNDER_TEST//,/ }; do # Split on comma
+  # Perform testing on main (with latest changes). Shallow copy as history is not important
+  git clone "https://github.com/googleapis/${repo}.git" --depth=1
+  pushd "${repo}"
+  # Install all repo modules to ~/.m2 (there can be multiple relevant artifacts to test i.e. core, admin, control)
+  mvn -B -ntp install -T 1C -DskipTests -Dclirr.skip -Denforcer.skip
+
+  linkage_checker_arguments=""
+  build_program_arguments "${repo}"
+
+  # Linkage Checker /dependencies
+  popd
+
+  echo "Artifact List: ${linkage_checker_arguments}"
+  # The `-s` argument filters the linkage check problems that stem from the artifact
+  program_args="-r --artifacts ${linkage_checker_arguments},com.google.protobuf:protobuf-java:${PROTOBUF_RUNTIME_VERSION},com.google.protobuf:protobuf-java-util:${PROTOBUF_RUNTIME_VERSION} -s ${linkage_checker_arguments}"
+  echo "Running Linkage Checker on the repo's handwritten modules"
+  echo "Linkage Checker Program Arguments: ${program_args}"
+  mvn -B -ntp exec:java -Dexec.args="${program_args}" -P exec-linkage-checker
+done
+popd
+popd
diff --git a/.kokoro/nightly/downstream-protobuf-source-compatibility.sh b/.kokoro/nightly/downstream-protobuf-source-compatibility.sh
index c7caeb724c..b718491689 100755
--- a/.kokoro/nightly/downstream-protobuf-source-compatibility.sh
+++ b/.kokoro/nightly/downstream-protobuf-source-compatibility.sh
@@ -15,20 +15,14 @@
 
 set -eo pipefail
 
-# Comma-delimited list of repos to test with the local java-shared-dependencies
-if [ -z "${REPOS_UNDER_TEST}" ]; then
-  echo "REPOS_UNDER_TEST must be set to run downstream-protobuf-source-compatibility.sh"
-  echo "Expects a comma-delimited list: i.e REPOS_UNDER_TEST=\"java-bigtable,java-bigquery\""
-  exit 1
-fi
+scriptDir=$(realpath "$(dirname "${BASH_SOURCE[0]}")")
+source "${scriptDir}/common.sh"
 
-# Version of Protobuf-Java runtime to compile with
-if [ -z "${PROTOBUF_RUNTIME_VERSION}" ]; then
-  echo "PROTOBUF_RUNTIME_VERSION must be set to run downstream-protobuf-source-compatibility.sh"
-  echo "Expects a single Protobuf-Java runtime version i.e. PROTOBUF_RUNTIME_VERSION=\"4.28.3\""
-  exit 1
-fi
+validate_protobuf_compatibility_script_inputs
 
+# REPOS_UNDER_TEST Env Var accepts a comma separated list of googleapis repos to test. For Github CI,
+# this will be a single repo as Github will build a matrix of repos with each repo being tested in parallel.
+# For local invocation, you can pass a list of repos to test multiple repos together.
 for repo in ${REPOS_UNDER_TEST//,/ }; do # Split on comma
   # Perform source-compatibility testing on main (latest changes)
   git clone "https://github.com/googleapis/$repo.git" --depth=1