diff --git a/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ClientCnx.java b/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ClientCnx.java
index eb39fe53f1ab6..9c6dcfa0effd8 100644
--- a/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ClientCnx.java
+++ b/pulsar-client/src/main/java/org/apache/pulsar/client/impl/ClientCnx.java
@@ -141,6 +141,9 @@ public class ClientCnx extends PulsarHandler {
 
     private final CompletableFuture<Void> connectionFuture = new CompletableFuture<Void>();
     private final ConcurrentLinkedQueue<RequestTime> requestTimeoutQueue = new ConcurrentLinkedQueue<>();
+
+    @VisibleForTesting
+    @Getter(AccessLevel.PACKAGE)
     private final Semaphore pendingLookupRequestSemaphore;
     private final Semaphore maxLookupRequestSemaphore;
     private final EventLoopGroup eventLoopGroup;
@@ -776,6 +779,11 @@ public CompletableFuture<LookupDataResult> newLookup(ByteBuf request, long reque
         TimedCompletableFuture<LookupDataResult> future = new TimedCompletableFuture<>();
 
         if (pendingLookupRequestSemaphore.tryAcquire()) {
+            future.whenComplete((lookupDataResult, throwable) -> {
+                if (throwable instanceof ConnectException) {
+                    pendingLookupRequestSemaphore.release();
+                }
+            });
             addPendingLookupRequests(requestId, future);
             ctx.writeAndFlush(request).addListener(writeFuture -> {
                 if (!writeFuture.isSuccess()) {
diff --git a/pulsar-client/src/test/java/org/apache/pulsar/client/impl/ClientCnxTest.java b/pulsar-client/src/test/java/org/apache/pulsar/client/impl/ClientCnxTest.java
index c6eba43fb7a16..63aa7b7048be0 100644
--- a/pulsar-client/src/test/java/org/apache/pulsar/client/impl/ClientCnxTest.java
+++ b/pulsar-client/src/test/java/org/apache/pulsar/client/impl/ClientCnxTest.java
@@ -34,6 +34,7 @@
 import io.netty.util.concurrent.DefaultThreadFactory;
 import java.lang.reflect.Field;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ThreadFactory;
 import java.util.function.Consumer;
@@ -50,6 +51,7 @@
 import org.apache.pulsar.common.protocol.Commands;
 import org.apache.pulsar.common.protocol.PulsarHandler;
 import org.apache.pulsar.common.util.netty.EventLoopUtil;
+import org.awaitility.Awaitility;
 import org.testng.annotations.Test;
 
 public class ClientCnxTest {
@@ -80,6 +82,70 @@ public void testClientCnxTimeout() throws Exception {
         eventLoop.shutdownGracefully();
     }
 
+    @Test
+    public void testPendingLookupRequestSemaphore() throws Exception {
+        EventLoopGroup eventLoop = EventLoopUtil.newEventLoopGroup(1, false, new DefaultThreadFactory("testClientCnxTimeout"));
+        ClientConfigurationData conf = new ClientConfigurationData();
+        conf.setOperationTimeoutMs(10_000);
+        conf.setKeepAliveIntervalSeconds(0);
+        ClientCnx cnx = new ClientCnx(conf, eventLoop);
+
+        ChannelHandlerContext ctx = mock(ChannelHandlerContext.class);
+        Channel channel = mock(Channel.class);
+        when(ctx.channel()).thenReturn(channel);
+        ChannelFuture listenerFuture = mock(ChannelFuture.class);
+        when(listenerFuture.addListener(any())).thenReturn(listenerFuture);
+        when(ctx.writeAndFlush(any())).thenReturn(listenerFuture);
+        cnx.channelActive(ctx);
+        CountDownLatch countDownLatch = new CountDownLatch(1);
+        CompletableFuture<Exception> completableFuture = new CompletableFuture<>();
+        new Thread(() -> {
+            try {
+                Thread.sleep(1_000);
+                CompletableFuture<BinaryProtoLookupService.LookupDataResult> future =
+                        cnx.newLookup(null, 123);
+                countDownLatch.countDown();
+                future.get();
+            } catch (Exception e) {
+                completableFuture.complete(e);
+            }
+        }).start();
+        countDownLatch.await();
+        cnx.channelInactive(ctx);
+        assertTrue(completableFuture.get().getCause() instanceof PulsarClientException.ConnectException);
+        // wait for subsequent calls over
+        Awaitility.await().untilAsserted(() -> {
+            assertEquals(cnx.getPendingLookupRequestSemaphore().availablePermits(), conf.getConcurrentLookupRequest());
+        });
+        eventLoop.shutdownGracefully();
+    }
+
+    @Test
+    public void testPendingWaitingLookupRequestSemaphore() throws Exception {
+        EventLoopGroup eventLoop = EventLoopUtil.newEventLoopGroup(1, false, new DefaultThreadFactory("testClientCnxTimeout"));
+        ClientConfigurationData conf = new ClientConfigurationData();
+        conf.setOperationTimeoutMs(10_000);
+        conf.setKeepAliveIntervalSeconds(0);
+        ClientCnx cnx = new ClientCnx(conf, eventLoop);
+
+        ChannelHandlerContext ctx = mock(ChannelHandlerContext.class);
+        Channel channel = mock(Channel.class);
+        when(ctx.channel()).thenReturn(channel);
+        ChannelFuture listenerFuture = mock(ChannelFuture.class);
+        when(listenerFuture.addListener(any())).thenReturn(listenerFuture);
+        when(ctx.writeAndFlush(any())).thenReturn(listenerFuture);
+        cnx.channelActive(ctx);
+        for (int i = 0; i < 5001; i++) {
+            cnx.newLookup(null, i);
+        }
+        cnx.channelInactive(ctx);
+        // wait for subsequent calls over
+        Awaitility.await().untilAsserted(() -> {
+            assertEquals(cnx.getPendingLookupRequestSemaphore().availablePermits(), conf.getConcurrentLookupRequest());
+        });
+        eventLoop.shutdownGracefully();
+    }
+
     @Test
     public void testReceiveErrorAtSendConnectFrameState() throws Exception {
         ThreadFactory threadFactory = new DefaultThreadFactory("testReceiveErrorAtSendConnectFrameState");