diff --git a/core/src/test/java/kafka/test/ClusterTestExtensionsTest.java b/core/src/test/java/kafka/test/ClusterTestExtensionsTest.java
index 0a0e3e29a55ce..f7d0b9c127e6e 100644
--- a/core/src/test/java/kafka/test/ClusterTestExtensionsTest.java
+++ b/core/src/test/java/kafka/test/ClusterTestExtensionsTest.java
@@ -32,7 +32,9 @@
 import org.junit.jupiter.api.extension.ExtendWith;
 
 
-@ClusterTestDefaults(clusterType = Type.ZK)   // Set defaults for a few params in @ClusterTest(s)
+@ClusterTestDefaults(clusterType = Type.ZK, serverProperties = {
+    @ClusterConfigProperty(key = "default.key", value = "default.value"),
+})   // Set defaults for a few params in @ClusterTest(s)
 @ExtendWith(ClusterTestExtensions.class)
 public class ClusterTestExtensionsTest {
 
@@ -89,20 +91,24 @@ public void testClusterTemplate() {
         }),
         @ClusterTest(name = "cluster-tests-2", clusterType = Type.KRAFT, serverProperties = {
             @ClusterConfigProperty(key = "foo", value = "baz"),
-            @ClusterConfigProperty(key = "spam", value = "eggz")
+            @ClusterConfigProperty(key = "spam", value = "eggz"),
+            @ClusterConfigProperty(key = "default.key", value = "overwrite.value")
         }),
         @ClusterTest(name = "cluster-tests-3", clusterType = Type.CO_KRAFT, serverProperties = {
             @ClusterConfigProperty(key = "foo", value = "baz"),
-            @ClusterConfigProperty(key = "spam", value = "eggz")
+            @ClusterConfigProperty(key = "spam", value = "eggz"),
+            @ClusterConfigProperty(key = "default.key", value = "overwrite.value")
         })
     })
     public void testClusterTests() {
         if (clusterInstance.clusterType().equals(ClusterInstance.ClusterType.ZK)) {
-            Assertions.assertEquals(clusterInstance.config().serverProperties().getProperty("foo"), "bar");
-            Assertions.assertEquals(clusterInstance.config().serverProperties().getProperty("spam"), "eggs");
+            Assertions.assertEquals("bar", clusterInstance.config().serverProperties().getProperty("foo"));
+            Assertions.assertEquals("eggs", clusterInstance.config().serverProperties().getProperty("spam"));
+            Assertions.assertEquals("default.value", clusterInstance.config().serverProperties().getProperty("default.key"));
         } else if (clusterInstance.clusterType().equals(ClusterInstance.ClusterType.RAFT)) {
-            Assertions.assertEquals(clusterInstance.config().serverProperties().getProperty("foo"), "baz");
-            Assertions.assertEquals(clusterInstance.config().serverProperties().getProperty("spam"), "eggz");
+            Assertions.assertEquals("baz", clusterInstance.config().serverProperties().getProperty("foo"));
+            Assertions.assertEquals("eggz", clusterInstance.config().serverProperties().getProperty("spam"));
+            Assertions.assertEquals("overwrite.value", clusterInstance.config().serverProperties().getProperty("default.key"));
         } else {
             Assertions.fail("Unknown cluster type " + clusterInstance.clusterType());
         }
diff --git a/core/src/test/java/kafka/test/annotation/ClusterTestDefaults.java b/core/src/test/java/kafka/test/annotation/ClusterTestDefaults.java
index cd8a66dfda03f..2f9efd777efc6 100644
--- a/core/src/test/java/kafka/test/annotation/ClusterTestDefaults.java
+++ b/core/src/test/java/kafka/test/annotation/ClusterTestDefaults.java
@@ -39,4 +39,6 @@
     int brokers() default 1;
     int controllers() default 1;
     boolean autoStart() default true;
+    // Set default server properties for all @ClusterTest(s)
+    ClusterConfigProperty[] serverProperties() default {};
 }
diff --git a/core/src/test/java/kafka/test/junit/ClusterTestExtensions.java b/core/src/test/java/kafka/test/junit/ClusterTestExtensions.java
index 8c838b279bdc8..39a16cd597777 100644
--- a/core/src/test/java/kafka/test/junit/ClusterTestExtensions.java
+++ b/core/src/test/java/kafka/test/junit/ClusterTestExtensions.java
@@ -34,7 +34,6 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
-import java.util.Properties;
 import java.util.function.Consumer;
 import java.util.stream.Stream;
 
@@ -189,13 +188,13 @@ private void processClusterTest(ExtensionContext context, ClusterTest annot, Clu
             builder.listenerName(annot.listener());
         }
 
-        Properties properties = new Properties();
+        ClusterConfig config = builder.build();
+        for (ClusterConfigProperty property : defaults.serverProperties()) {
+            config.serverProperties().put(property.key(), property.value());
+        }
         for (ClusterConfigProperty property : annot.serverProperties()) {
-            properties.put(property.key(), property.value());
+            config.serverProperties().put(property.key(), property.value());
         }
-
-        ClusterConfig config = builder.build();
-        config.serverProperties().putAll(properties);
         type.invocationContexts(context.getRequiredTestMethod().getName(), config, testInvocations);
     }