diff --git a/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterClientProtocol.java b/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterClientProtocol.java
index 41454458eb8fa..30c09ce52c362 100644
--- a/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterClientProtocol.java
+++ b/hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterClientProtocol.java
@@ -22,6 +22,7 @@
 import static org.apache.hadoop.hdfs.server.federation.router.FederationUtil.updateMountPointStatus;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.crypto.CryptoProtocolVersion;
+import org.apache.hadoop.fs.BatchedRemoteIterator;
 import org.apache.hadoop.fs.BatchedRemoteIterator.BatchedEntries;
 import org.apache.hadoop.fs.CacheFlag;
 import org.apache.hadoop.fs.ContentSummary;
@@ -1977,8 +1978,45 @@ public BatchedEntries<OpenFileEntry> listOpenFiles(long prevId)
   public BatchedEntries<OpenFileEntry> listOpenFiles(long prevId,
       EnumSet<OpenFilesIterator.OpenFilesType> openFilesTypes, String path)
           throws IOException {
-    rpcServer.checkOperation(NameNode.OperationCategory.READ, false);
-    return null;
+    rpcServer.checkOperation(NameNode.OperationCategory.READ, true);
+    List<RemoteLocation> locations = rpcServer.getLocationsForPath(path, false, false);
+    RemoteMethod method =
+        new RemoteMethod("listOpenFiles", new Class<?>[] {long.class, EnumSet.class, String.class},
+            prevId, openFilesTypes, new RemoteParam());
+    Map<RemoteLocation, BatchedEntries> results =
+        rpcClient.invokeConcurrent(locations, method, true, false, -1, BatchedEntries.class);
+
+    // Get the largest inodeIds for each namespace, and the smallest inodeId of them
+    // then ignore all entries above this id to keep a consistent prevId for the next listOpenFiles
+    long minOfMax = Long.MAX_VALUE;
+    for (BatchedEntries nsEntries : results.values()) {
+      // Only need to care about namespaces that still have more files to report
+      if (!nsEntries.hasMore()) {
+        continue;
+      }
+      long max = 0;
+      for (int i = 0; i < nsEntries.size(); i++) {
+        max = Math.max(max, ((OpenFileEntry) nsEntries.get(i)).getId());
+      }
+      minOfMax = Math.min(minOfMax, max);
+    }
+    // Concatenate all entries into one result, sorted by inodeId
+    List<OpenFileEntry> routerEntries = new ArrayList<>();
+    boolean hasMore = false;
+    for (Map.Entry<RemoteLocation, BatchedEntries> entry : results.entrySet()) {
+      BatchedEntries nsEntries = entry.getValue();
+      hasMore |= nsEntries.hasMore();
+      for (int i = 0; i < nsEntries.size(); i++) {
+        OpenFileEntry ofe = (OpenFileEntry) nsEntries.get(i);
+        if (ofe.getId() > minOfMax) {
+          hasMore = true;
+          break;
+        }
+        routerEntries.add(ofe);
+      }
+    }
+    routerEntries.sort(Comparator.comparingLong(OpenFileEntry::getId));
+    return new BatchedRemoteIterator.BatchedListEntries<>(routerEntries, hasMore);
   }
 
   @Override
diff --git a/hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/router/TestRouterListOpenFiles.java b/hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/router/TestRouterListOpenFiles.java
new file mode 100644
index 0000000000000..b82826c249528
--- /dev/null
+++ b/hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/router/TestRouterListOpenFiles.java
@@ -0,0 +1,214 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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.
+ */
+package org.apache.hadoop.hdfs.server.federation.router;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.EnumSet;
+import java.util.List;
+
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.BatchedRemoteIterator;
+import org.apache.hadoop.fs.RemoteIterator;
+import org.apache.hadoop.hdfs.DFSClient;
+import org.apache.hadoop.hdfs.DFSConfigKeys;
+import org.apache.hadoop.hdfs.protocol.OpenFileEntry;
+import org.apache.hadoop.hdfs.protocol.OpenFilesIterator;
+import org.apache.hadoop.hdfs.server.federation.MiniRouterDFSCluster;
+import org.apache.hadoop.hdfs.server.federation.RouterConfigBuilder;
+import org.apache.hadoop.hdfs.server.federation.StateStoreDFSCluster;
+import org.apache.hadoop.hdfs.server.federation.resolver.MultipleDestinationMountTableResolver;
+import org.apache.hadoop.hdfs.server.federation.resolver.order.DestinationOrder;
+
+import static org.apache.hadoop.hdfs.server.federation.FederationTestUtils.createMountTableEntry;
+import static org.apache.hadoop.test.GenericTestUtils.getMethodName;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class TestRouterListOpenFiles {
+  final private static int NUM_SUBCLUSTERS = 2;
+  final private static int BATCH_SIZE = 3;
+  private static StateStoreDFSCluster cluster;
+  private static MiniRouterDFSCluster.RouterContext routerContext;
+  private static RouterClientProtocol routerProtocol;
+  private static DFSClient client0;
+  private static DFSClient client1;
+  private static DFSClient routerClient;
+
+  @BeforeAll
+  public static void setup() throws Exception {
+    cluster = new StateStoreDFSCluster(false, NUM_SUBCLUSTERS,
+        MultipleDestinationMountTableResolver.class);
+    Configuration conf = new RouterConfigBuilder().stateStore().heartbeat().admin().rpc().build();
+    conf.set(RBFConfigKeys.DFS_ROUTER_MONITOR_NAMENODE, "ns0,ns1");
+    conf.setBoolean(RBFConfigKeys.MOUNT_TABLE_CACHE_UPDATE, true);
+    conf.setInt(DFSConfigKeys.DFS_NAMENODE_LIST_OPENFILES_NUM_RESPONSES, BATCH_SIZE);
+    cluster.addRouterOverrides(conf);
+    cluster.startCluster(conf);
+    cluster.startRouters();
+    cluster.waitClusterUp();
+    routerContext = cluster.getRandomRouter();
+    routerProtocol = routerContext.getRouterRpcServer().getClientProtocolModule();
+    routerClient = routerContext.getClient();
+    client0 = cluster.getNamenode("ns0", null).getClient();
+    client1 = cluster.getNamenode("ns1", null).getClient();
+  }
+
+  @AfterAll
+  public static void cleanup() {
+    if (cluster != null) {
+      cluster.shutdown();
+      cluster = null;
+    }
+  }
+
+  @BeforeEach
+  public void resetInodeId() {
+    cluster.getNamenode("ns0", null).getNamenode().getNamesystem().getFSDirectory()
+        .resetLastInodeIdWithoutChecking(12345);
+    cluster.getNamenode("ns1", null).getNamenode().getNamesystem().getFSDirectory()
+        .resetLastInodeIdWithoutChecking(12345);
+  }
+
+  @Test
+  public void testSingleDestination() throws Exception {
+    String testPath = "/" + getMethodName();
+    createMountTableEntry(routerContext.getRouter(), testPath, DestinationOrder.HASH,
+        Collections.singletonList("ns0"));
+
+    // Create 2 dirs with the same name on 2 different nss
+    client0.mkdirs(testPath);
+    client1.mkdirs(testPath);
+    // Open 2 files with different names
+    OutputStream os0 = client0.create(testPath + "/file0", true);
+    OutputStream os1 = client1.create(testPath + "/file1", true);
+
+    BatchedRemoteIterator.BatchedEntries<OpenFileEntry> result =
+        routerProtocol.listOpenFiles(0, EnumSet.of(OpenFilesIterator.OpenFilesType.ALL_OPEN_FILES),
+            testPath);
+    // Should list only the entry on ns0
+    assertEquals(1, result.size());
+    assertEquals(testPath + "/file0", result.get(0).getFilePath());
+    os0.close();
+    os1.close();
+  }
+
+  @Test
+  public void testMultipleDestinations() throws Exception {
+    String testPath = "/" + getMethodName();
+    createMountTableEntry(routerContext.getRouter(), testPath, DestinationOrder.HASH_ALL,
+        cluster.getNameservices());
+
+    // Create 2 dirs with the same name on 2 different nss
+    client0.mkdirs(testPath);
+    client1.mkdirs(testPath);
+
+    // Open 2 files with different names
+    OutputStream os0 = client0.create(testPath + "/file0", true);
+    OutputStream os1 = client1.create(testPath + "/file1", true);
+    BatchedRemoteIterator.BatchedEntries<OpenFileEntry> result =
+        routerProtocol.listOpenFiles(0, EnumSet.of(OpenFilesIterator.OpenFilesType.ALL_OPEN_FILES),
+            testPath);
+    // Should list both entries on ns0 and ns1
+    assertEquals(2, result.size());
+    assertEquals(testPath + "/file0", result.get(0).getFilePath());
+    assertEquals(testPath + "/file1", result.get(1).getFilePath());
+    RemoteIterator<OpenFileEntry> ite = routerClient.listOpenFiles(testPath);
+    while (ite.hasNext()) {
+      OpenFileEntry ofe = ite.next();
+      assertTrue(ofe.getFilePath().equals(testPath + "/file0") || ofe.getFilePath()
+          .equals(testPath + "/file1"));
+    }
+    os0.close();
+    os1.close();
+
+    // Open 2 files with same name
+    os0 = client0.create(testPath + "/file2", true);
+    os1 = client1.create(testPath + "/file2", true);
+    result =
+        routerProtocol.listOpenFiles(0, EnumSet.of(OpenFilesIterator.OpenFilesType.ALL_OPEN_FILES),
+            testPath);
+    // Should list both entries
+    assertEquals(2, result.size());
+    assertEquals(testPath + "/file2", result.get(0).getFilePath());
+    assertEquals(testPath + "/file2", result.get(1).getFilePath());
+    ite = routerClient.listOpenFiles(testPath);
+    while (ite.hasNext()) {
+      OpenFileEntry ofe = ite.next();
+      assertTrue(ofe.getFilePath().equals(testPath + "/file2"));
+    }
+    os0.close();
+    os1.close();
+  }
+
+  @Test
+  public void testMultipleDestinationsMultipleBatches() throws Exception {
+    String testPath = "/" + getMethodName();
+    createMountTableEntry(routerContext.getRouter(), testPath, DestinationOrder.HASH_ALL,
+        cluster.getNameservices());
+
+    // Make ns1 have a much bigger inodeid than ns0
+    cluster.getNamenode("ns0", null).getNamenode().getNamesystem().getFSDirectory()
+        .resetLastInodeIdWithoutChecking((long) 1E6);
+    cluster.getNamenode("ns1", null).getNamenode().getNamesystem().getFSDirectory()
+        .resetLastInodeIdWithoutChecking((long) 2E6);
+    runBatchListOpenFilesTest(testPath);
+
+    // Rerun the test with ns0 having a much bigger inodeid than ns1
+    cluster.getNamenode("ns0", null).getNamenode().getNamesystem().getFSDirectory()
+        .resetLastInodeIdWithoutChecking((long) 4E6);
+    cluster.getNamenode("ns1", null).getNamenode().getNamesystem().getFSDirectory()
+        .resetLastInodeIdWithoutChecking((long) 3E6);
+    runBatchListOpenFilesTest(testPath);
+  }
+
+  private static void runBatchListOpenFilesTest(String testPath) throws IOException {
+    // Create 2 dirs with the same name on 2 different nss
+    client0.mkdirs(testPath);
+    client1.mkdirs(testPath);
+    // Open 3 batches on both namespaces
+    OutputStream[] oss0 = new OutputStream[3 * BATCH_SIZE];
+    OutputStream[] oss1 = new OutputStream[3 * BATCH_SIZE];
+    for (int i = 0; i < 3 * BATCH_SIZE; i++) {
+      oss0[i] = client0.create(testPath + "/file0a_" + i, true);
+      oss1[i] = client1.create(testPath + "/file1a_" + i, true);
+    }
+    RemoteIterator<OpenFileEntry> ite = routerClient.listOpenFiles(testPath);
+    List<OpenFileEntry> allEntries = new ArrayList<>();
+    while (ite.hasNext()) {
+      allEntries.add(ite.next());
+    }
+    // All files should be reported once
+    assertEquals(3 * 2 * BATCH_SIZE, allEntries.size());
+
+    // Clean up
+    for (int i = 0; i < 3 * BATCH_SIZE; i++) {
+      oss0[i].close();
+      oss1[i].close();
+    }
+    client0.delete(testPath, true);
+    client1.delete(testPath, true);
+  }
+}
diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java
index dd6e021a80d31..1e18ae1eae639 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirectory.java
@@ -2060,8 +2060,12 @@ void resetLastInodeId(long newValue) throws IOException {
     }
   }
 
-  /** Should only be used for tests to reset to any value */
-  void resetLastInodeIdWithoutChecking(long newValue) {
+  /**
+   * Should only be used for tests to reset to any value.
+   * @param newValue new value to set to
+   */
+  @VisibleForTesting
+  public void resetLastInodeIdWithoutChecking(long newValue) {
     inodeId.setCurrentValue(newValue);
   }