diff --git a/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentTopic.java b/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentTopic.java
index 03adb2a9c5ed5..e7a006185af77 100644
--- a/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentTopic.java
+++ b/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentTopic.java
@@ -1277,8 +1277,7 @@ public CompletableFuture<Void> unsubscribe(String subscriptionName) {
         CompletableFuture<Void> unsubscribeFuture = new CompletableFuture<>();
 
         TopicName tn = TopicName.get(MLPendingAckStore
-                .getTransactionPendingAckStoreSuffix(topic,
-                        Codec.encode(subscriptionName)));
+                .getTransactionPendingAckStoreSuffix(topic, subscriptionName));
         if (brokerService.pulsar().getConfiguration().isTransactionCoordinatorEnabled()) {
             ManagedLedgerConfig managedLedgerConfig = ledger.getConfig();
                 ManagedLedgerFactory managedLedgerFactory = getBrokerService()
diff --git a/pulsar-broker/src/main/java/org/apache/pulsar/broker/transaction/pendingack/impl/MLPendingAckStore.java b/pulsar-broker/src/main/java/org/apache/pulsar/broker/transaction/pendingack/impl/MLPendingAckStore.java
index 25c7727259db3..b4f63bf64c132 100644
--- a/pulsar-broker/src/main/java/org/apache/pulsar/broker/transaction/pendingack/impl/MLPendingAckStore.java
+++ b/pulsar-broker/src/main/java/org/apache/pulsar/broker/transaction/pendingack/impl/MLPendingAckStore.java
@@ -59,6 +59,7 @@
 import org.apache.pulsar.common.api.proto.CommandAck.AckType;
 import org.apache.pulsar.common.naming.SystemTopicNames;
 import org.apache.pulsar.common.naming.TopicName;
+import org.apache.pulsar.common.util.Codec;
 import org.apache.pulsar.transaction.coordinator.impl.TxnBatchedPositionImpl;
 import org.apache.pulsar.transaction.coordinator.impl.TxnLogBufferedWriter;
 import org.apache.pulsar.transaction.coordinator.impl.TxnLogBufferedWriterConfig;
@@ -516,7 +517,13 @@ public CompletableFuture<ManagedLedger> getManagedLedger() {
     }
 
     public static String getTransactionPendingAckStoreSuffix(String originTopicName, String subName) {
-        return TopicName.get(originTopicName) + "-" + subName + SystemTopicNames.PENDING_ACK_STORE_SUFFIX;
+        // URL-encode the subscription name so that any '/' characters it contains do not create
+        // extra path segments when the resulting string is parsed as a topic name.  TopicName
+        // always decodes the local-name component on parse (via Codec.decode) and re-encodes it
+        // on output (via getEncodedLocalName / getPersistenceNamingEncoding), so encoding here
+        // produces a valid round-trip with no double-encoding.
+        String encodedSubName = Codec.encode(subName);
+        return TopicName.get(originTopicName) + "-" + encodedSubName + SystemTopicNames.PENDING_ACK_STORE_SUFFIX;
     }
 
     public static String getTransactionPendingAckStoreCursorName() {
@@ -569,4 +576,4 @@ public ByteBuf serialize(ArrayList<PendingAckMetadataEntry> dataArray) {
             return buf;
         }
     }
-}
\ No newline at end of file
+}
diff --git a/pulsar-broker/src/test/java/org/apache/pulsar/broker/transaction/pendingack/impl/MLPendingAckStoreTest.java b/pulsar-broker/src/test/java/org/apache/pulsar/broker/transaction/pendingack/impl/MLPendingAckStoreTest.java
index 154cbe39d408c..14e1ceade5036 100644
--- a/pulsar-broker/src/test/java/org/apache/pulsar/broker/transaction/pendingack/impl/MLPendingAckStoreTest.java
+++ b/pulsar-broker/src/test/java/org/apache/pulsar/broker/transaction/pendingack/impl/MLPendingAckStoreTest.java
@@ -45,6 +45,9 @@
 import org.apache.pulsar.client.api.transaction.TxnID;
 import org.apache.pulsar.common.api.proto.CommandAck;
 import org.apache.pulsar.common.api.proto.CommandSubscribe;
+import org.apache.pulsar.common.naming.SystemTopicNames;
+import org.apache.pulsar.common.naming.TopicName;
+import org.apache.pulsar.common.util.Codec;
 import org.apache.pulsar.common.util.FutureUtil;
 import org.apache.pulsar.transaction.coordinator.impl.TxnLogBufferedWriterConfig;
 import org.awaitility.Awaitility;
@@ -140,6 +143,33 @@ private MLPendingAckStore createPendingAckStore(TxnLogBufferedWriterConfig txnLo
         return (MLPendingAckStore) mlPendingAckStoreProvider.newPendingAckStore(persistentSubscriptionMock).get();
     }
 
+    @Test
+    public void testPendingAckStoreWithSlashSubscriptionName() throws Exception {
+        String slashSubName = "tenant/namespace/my-function";
+        when(persistentSubscriptionMock.getName()).thenReturn(slashSubName);
+
+        MLPendingAckStoreProvider provider = new MLPendingAckStoreProvider();
+
+        // Should not throw — subscription names containing '/' must be URL-encoded so the
+        // resulting pending-ack topic name is a valid V2 persistent topic name.
+        MLPendingAckStore store = (MLPendingAckStore) provider.newPendingAckStore(persistentSubscriptionMock).get();
+
+        // Verify the managed ledger persistence path encodes the subscription name correctly.
+        // Expected: tenant/namespace/persistent/<encodedLocalName>
+        // where localName = "<topic>-<encodedSubName>__transaction_pending_ack"
+        String originTopicName = persistentSubscriptionMock.getTopic().getName();
+        TopicName origin = TopicName.get(originTopicName);
+        String encodedSubName = Codec.encode(slashSubName);
+        String expectedLocalName = origin.getLocalName() + "-" + encodedSubName
+                + SystemTopicNames.PENDING_ACK_STORE_SUFFIX;
+        // getPersistenceNamingEncoding() = tenant/namespace/persistent/encodedLocalName
+        String expectedMlName = origin.getTenant() + "/" + origin.getNamespacePortion()
+                + "/persistent/" + Codec.encode(expectedLocalName);
+        Assert.assertEquals(store.getManagedLedger().get().getName(), expectedMlName);
+
+        closePendingAckStoreWithRetry(store);
+    }
+
     /**
      * Overridden cases:
      *   1. Batched write and replay with batched feature.