diff --git a/hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/OmMetadataManagerImpl.java b/hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/OmMetadataManagerImpl.java
index bdc31e5f155e..9164d480d493 100644
--- a/hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/OmMetadataManagerImpl.java
+++ b/hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/OmMetadataManagerImpl.java
@@ -804,13 +804,16 @@ public List<RepeatedOmKeyInfo> listTrash(String volumeName, String bucketName,
     return deletedKeys;
   }
 
+  /**
+   * @param userName volume owner, null for listing all volumes.
+   */
   @Override
   public List<OmVolumeArgs> listVolumes(String userName,
       String prefix, String startKey, int maxKeys) throws IOException {
 
     if (StringUtil.isBlank(userName)) {
-      throw new OMException("User name is required to list Volumes.",
-          ResultCodes.USER_NOT_FOUND);
+      // null userName represents listing all volumes in cluster.
+      return listAllVolumes(prefix, startKey, maxKeys);
     }
 
     final List<OmVolumeArgs> result = Lists.newArrayList();
@@ -850,6 +853,44 @@ public List<OmVolumeArgs> listVolumes(String userName,
     return result;
   }
 
+    /**
+     * @return list of all volumes.
+     */
+  private List<OmVolumeArgs> listAllVolumes(String prefix, String startKey,
+      int maxKeys) {
+    List<OmVolumeArgs> result = Lists.newArrayList();
+
+    /* volumeTable is full-cache, so we use cacheIterator. */
+    Iterator<Map.Entry<CacheKey<String>, CacheValue<OmVolumeArgs>>>
+        cacheIterator = getVolumeTable().cacheIterator();
+
+    String volumeName;
+    OmVolumeArgs omVolumeArgs;
+    boolean prefixIsEmpty = Strings.isNullOrEmpty(prefix);
+    boolean startKeyIsEmpty = Strings.isNullOrEmpty(startKey);
+    while (cacheIterator.hasNext() && result.size() < maxKeys) {
+      Map.Entry<CacheKey<String>, CacheValue<OmVolumeArgs>> entry =
+          cacheIterator.next();
+      omVolumeArgs = entry.getValue().getCacheValue();
+      volumeName = omVolumeArgs.getVolume();
+
+      if (!prefixIsEmpty && !volumeName.startsWith(prefix)) {
+        continue;
+      }
+
+      if (!startKeyIsEmpty) {
+        if (volumeName.equals(startKey)) {
+          startKeyIsEmpty = true;
+        }
+        continue;
+      }
+
+      result.add(omVolumeArgs);
+    }
+
+    return result;
+  }
+
   private UserVolumeInfo getVolumesByUser(String userNameKey)
       throws OMException {
     try {
diff --git a/hadoop-ozone/ozone-manager/src/test/java/org/apache/hadoop/ozone/om/TestOmMetadataManager.java b/hadoop-ozone/ozone-manager/src/test/java/org/apache/hadoop/ozone/om/TestOmMetadataManager.java
index 6802afcd620e..dc2187ccec87 100644
--- a/hadoop-ozone/ozone-manager/src/test/java/org/apache/hadoop/ozone/om/TestOmMetadataManager.java
+++ b/hadoop-ozone/ozone-manager/src/test/java/org/apache/hadoop/ozone/om/TestOmMetadataManager.java
@@ -89,6 +89,54 @@ public void testListVolumes() throws Exception {
     Assert.assertEquals(volumeList.size(), totalVol - startOrder - 1);
   }
 
+  @Test
+  public void testListAllVolumes() throws Exception {
+    OmVolumeArgs.Builder argsBuilder =
+        OmVolumeArgs.newBuilder().setAdminName("admin");
+    String volName;
+    String ownerName;
+    for (int i = 0; i < 50; i++) {
+      ownerName = "owner" + i;
+      volName = "vola" + i;
+      OmVolumeArgs omVolumeArgs = argsBuilder.
+          setOwnerName(ownerName).setVolume(volName).build();
+      TestOMRequestUtils.addVolumeToOM(omMetadataManager, omVolumeArgs);
+      TestOMRequestUtils.addUserToDB(volName, ownerName, omMetadataManager);
+    }
+    for (int i = 0; i < 50; i++) {
+      ownerName = "owner" + i;
+      volName = "volb" + i;
+      OmVolumeArgs omVolumeArgs = argsBuilder.
+          setOwnerName(ownerName).setVolume(volName).build();
+      TestOMRequestUtils.addVolumeToOM(omMetadataManager, omVolumeArgs);
+      TestOMRequestUtils.addUserToDB(volName, ownerName, omMetadataManager);
+    }
+
+    String prefix = "";
+    String startKey = "";
+
+    // Test list all volumes
+    List<OmVolumeArgs> volListA = omMetadataManager.listVolumes(null,
+        prefix, startKey, 1000);
+    Assert.assertEquals(volListA.size(), 100);
+
+    // Test list all volumes with prefix
+    prefix = "volb";
+    List<OmVolumeArgs> volListB = omMetadataManager.listVolumes(null,
+        prefix, startKey, 1000);
+    Assert.assertEquals(volListB.size(), 50);
+
+    // Test list all volumes with setting startVolume
+    // that was not part of result.
+    prefix = "";
+    int totalVol = volListB.size();
+    int startOrder = 0;
+    startKey = "volb" + startOrder;
+    List<OmVolumeArgs> volListC = omMetadataManager.listVolumes(null,
+        prefix, startKey, 1000);
+    Assert.assertEquals(volListC.size(), totalVol - startOrder - 1);
+  }
+
   @Test
   public void testListBuckets() throws Exception {