diff --git a/.scala-steward.conf b/.scala-steward.conf
index afb66961..056620aa 100644
--- a/.scala-steward.conf
+++ b/.scala-steward.conf
@@ -15,9 +15,6 @@ updates.pin = [
 
   # Scala 3.3 is a LTS
   { groupId = "org.scala-lang", artifactId = "scala3-library", version = "3.3." }
-  # when we update to protobuf 4.x we probably need to update a bunch of libraries
-  # in tandem, and possibly schedule this for a major pekko-grpc release
-  { groupId = "com.google.protobuf", version = "3." }
 
   # Issues when using GRPC 1.68+ - https://github.com/apache/pekko-grpc/pull/397
   { groupId = "io.grpc", version = "1.67." }
diff --git a/build.sbt b/build.sbt
index 4986ba78..d1a70bf9 100644
--- a/build.sbt
+++ b/build.sbt
@@ -20,6 +20,7 @@ sourceDistName := "apache-pekko-grpc"
 sourceDistIncubating := false
 ThisBuild / versionScheme := Some(VersionScheme.SemVerSpec)
 ThisBuild / resolvers += Resolver.ApacheMavenStagingRepo
+ThisBuild / resolvers ++= Resolver.sonatypeOssRepos("snapshots")
 
 commands := commands.value.filterNot { command =>
   command.nameOption.exists { name =>
@@ -291,6 +292,7 @@ lazy val pluginTesterScala = Project(id = "plugin-tester-scala", base = file("pl
     fork := true,
     crossScalaVersions := Dependencies.Versions.CrossScalaForLib,
     scalaVersion := scala212,
+    PB.protocVersion := Dependencies.Versions.googleProtoc,
     ReflectiveCodeGen.codeGeneratorSettings ++= Seq("flat_package", "server_power_apis"))
   .pluginTestingSettings
   .enablePlugins(NoPublish)
diff --git a/gradle-plugin/src/main/groovy/org/apache/pekko/grpc/gradle/PekkoGrpcPluginExtension.groovy b/gradle-plugin/src/main/groovy/org/apache/pekko/grpc/gradle/PekkoGrpcPluginExtension.groovy
index 74d4a12c..3fa6b8c6 100644
--- a/gradle-plugin/src/main/groovy/org/apache/pekko/grpc/gradle/PekkoGrpcPluginExtension.groovy
+++ b/gradle-plugin/src/main/groovy/org/apache/pekko/grpc/gradle/PekkoGrpcPluginExtension.groovy
@@ -14,7 +14,7 @@ import org.gradle.api.Project
 
 class PekkoGrpcPluginExtension {
 
-    static final String PROTOC_VERSION = "3.25.5" // checked synced by VersionSyncCheckPlugin
+    static final String PROTOC_VERSION = "4.28.2" // checked synced by VersionSyncCheckPlugin
 
     static final String PROTOC_PLUGIN_SCALA_VERSION = "2.12"
 
diff --git a/maven-plugin/src/main/maven/plugin.xml b/maven-plugin/src/main/maven/plugin.xml
index 18a8bc38..9bf1470f 100644
--- a/maven-plugin/src/main/maven/plugin.xml
+++ b/maven-plugin/src/main/maven/plugin.xml
@@ -95,7 +95,7 @@
         <extraGenerators implementation="java.util.List" default-value=""/>
         <protoPaths default-value="${project.basedir}/src/main/proto,${project.basedir}/src/main/protobuf">${pekko-grpc.protoPaths}</protoPaths>
         <outputDirectory default-value="${project.build.directory}/generated-sources">${pekko-grpc.outputDirectory}</outputDirectory>
-	<protocVersion implementation="java.lang.String" default-value="-v3.25.5">${pekko-grpc.protoc-version}</protocVersion> <!-- checked synced by VersionSyncCheckPlugin -->
+	<protocVersion implementation="java.lang.String" default-value="-v4.28.2">${pekko-grpc.protoc-version}</protocVersion> <!-- checked synced by VersionSyncCheckPlugin -->
         <includeStdTypes implementation="boolean" default-value="false" />
       </configuration>
     </mojo>
@@ -187,7 +187,7 @@
         <extraGenerators implementation="java.util.List" default-value=""/>
         <protoPaths default-value="src/test/proto,src/test/protobuf">${pekko-grpc.protoPaths}</protoPaths>
         <outputDirectory default-value="target/generated-test-sources">${pekko-grpc.outputDirectory}</outputDirectory>
-        <protocVersion implementation="java.lang.String" default-value="-v3.25.5">${pekko-grpc.protoc-version}</protocVersion> <!-- checked synced by VersionSyncCheckPlugin -->
+        <protocVersion implementation="java.lang.String" default-value="-v4.28.2">${pekko-grpc.protoc-version}</protocVersion> <!-- checked synced by VersionSyncCheckPlugin -->
         <includeStdTypes implementation="boolean" default-value="false" />
       </configuration>
     </mojo>
diff --git a/plugin-tester-scala/build.gradle b/plugin-tester-scala/build.gradle
index 42edf46a..67b1ed60 100644
--- a/plugin-tester-scala/build.gradle
+++ b/plugin-tester-scala/build.gradle
@@ -26,6 +26,7 @@ def scalaBinaryVersion = "${scalaVersion.major}.${scalaVersion.minor}"
 dependencies {
   implementation "org.apache.pekko:pekko-http-cors_${scalaBinaryVersion}:1.1.0"
   implementation "org.scala-lang:scala-library:${scalaFullVersion}"
+  implementation 'com.google.protobuf:protobuf-java:4.28.2'
   testImplementation "org.apache.pekko:pekko-stream-testkit_${scalaBinaryVersion}:1.1.2"
   testImplementation "org.scalatest:scalatest_${scalaBinaryVersion}:3.2.19"
   testImplementation "org.scalatestplus:junit-4-13_${scalaBinaryVersion}:3.2.19.0"
diff --git a/project/Dependencies.scala b/project/Dependencies.scala
index 319b5480..ad6f05ca 100644
--- a/project/Dependencies.scala
+++ b/project/Dependencies.scala
@@ -36,8 +36,8 @@ object Dependencies {
     // Even referenced explicitly in the sbt-plugin's sbt-tests
     // If changing this, remember to update protoc plugin version to align in
     // maven-plugin/src/main/maven/plugin.xml and org.apache.pekko.grpc.sbt.PekkoGrpcPlugin
-    val googleProtoc = "3.25.5" // checked synced by VersionSyncCheckPlugin
-    val googleProtobufJava = "3.25.5"
+    val googleProtobufJava = "4.28.2"
+    val googleProtoc = googleProtobufJava // checked synced by VersionSyncCheckPlugin
 
     val scalaTest = "3.2.19"
 
@@ -130,5 +130,6 @@ object Dependencies {
     Compile.grpcStub,
     Test.scalaTest,
     Test.scalaTestPlusJunit,
+    Protobuf.protobufJava,
     Protobuf.googleCommonProtos)
 }
diff --git a/project/plugins.sbt b/project/plugins.sbt
index fbb8be43..8afc8f49 100644
--- a/project/plugins.sbt
+++ b/project/plugins.sbt
@@ -41,4 +41,4 @@ libraryDependencies += "org.eclipse.jgit" % "org.eclipse.jgit" % "5.13.3.2024011
 // scripted testing
 libraryDependencies += "org.scala-sbt" %% "scripted-plugin" % sbtVersion.value
 
-libraryDependencies += "com.thesamet.scalapb" %% "compilerplugin" % "0.11.17"
+libraryDependencies += "com.thesamet.scalapb" %% "compilerplugin" % "1.0.0-alpha.1"