diff --git a/vertx-sql-client/src/main/java/io/vertx/sqlclient/impl/pool/SqlConnectionPool.java b/vertx-sql-client/src/main/java/io/vertx/sqlclient/impl/pool/SqlConnectionPool.java
index 113cec157..63eb5e658 100644
--- a/vertx-sql-client/src/main/java/io/vertx/sqlclient/impl/pool/SqlConnectionPool.java
+++ b/vertx-sql-client/src/main/java/io/vertx/sqlclient/impl/pool/SqlConnectionPool.java
@@ -279,8 +279,10 @@ public void complete(Lease<PooledConnection> lease, Throwable failure) {
                 if (ar2.succeeded()) {
                   handle(lease);
                 } else {
-                  // Should we do some cleanup ?
-                  handler.fail(failure);
+                  // return the lease to the pool, otherwise its slot leaks forever
+                  lease.recycle();
+                  dequeueMetric(metric);
+                  handler.fail(ar2.cause());
                 }
               });
             } else {
diff --git a/vertx-sql-client/src/test/java/io/vertx/tests/sqlclient/SqlConnectionPoolAcquireHookTest.java b/vertx-sql-client/src/test/java/io/vertx/tests/sqlclient/SqlConnectionPoolAcquireHookTest.java
new file mode 100644
index 000000000..13c670b22
--- /dev/null
+++ b/vertx-sql-client/src/test/java/io/vertx/tests/sqlclient/SqlConnectionPoolAcquireHookTest.java
@@ -0,0 +1,161 @@
+/*
+ * Copyright (c) 2011-2026 Contributors to the Eclipse Foundation
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
+ * which is available at https://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
+ */
+
+package io.vertx.tests.sqlclient;
+
+import io.vertx.core.Completable;
+import io.vertx.core.Context;
+import io.vertx.core.Future;
+import io.vertx.core.Vertx;
+import io.vertx.core.internal.ContextInternal;
+import io.vertx.core.internal.VertxInternal;
+import io.vertx.core.net.SocketAddress;
+import io.vertx.core.spi.metrics.ClientMetrics;
+import io.vertx.core.tracing.TracingPolicy;
+import io.vertx.ext.unit.Async;
+import io.vertx.ext.unit.TestContext;
+import io.vertx.ext.unit.junit.VertxUnitRunner;
+import io.vertx.sqlclient.SqlConnectOptions;
+import io.vertx.sqlclient.impl.pool.SqlConnectionPool;
+import io.vertx.sqlclient.spi.DatabaseMetadata;
+import io.vertx.sqlclient.spi.connection.Connection;
+import io.vertx.sqlclient.spi.connection.ConnectionContext;
+import io.vertx.sqlclient.spi.connection.ConnectionFactory;
+import io.vertx.sqlclient.spi.protocol.CommandBase;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * When the {@code afterAcquire} hook fails, the acquisition must fail with the hook failure and
+ * the lease must be returned to the pool, otherwise the slot leaks and the pool eventually starves.
+ */
+@RunWith(VertxUnitRunner.class)
+public class SqlConnectionPoolAcquireHookTest {
+
+  static class StubConnection implements Connection {
+
+    @Override
+    public TracingPolicy tracingPolicy() {
+      return TracingPolicy.IGNORE;
+    }
+
+    @Override
+    public ClientMetrics metrics() {
+      return null;
+    }
+
+    @Override
+    public SocketAddress server() {
+      return SocketAddress.inetSocketAddress(5432, "localhost");
+    }
+
+    @Override
+    public String database() {
+      return "db";
+    }
+
+    @Override
+    public String user() {
+      return "user";
+    }
+
+    @Override
+    public void init(ConnectionContext context) {
+    }
+
+    @Override
+    public void close(ConnectionContext holder, Completable<Void> promise) {
+      promise.succeed();
+    }
+
+    @Override
+    public boolean isSsl() {
+      return false;
+    }
+
+    @Override
+    public boolean isValid() {
+      return true;
+    }
+
+    @Override
+    public DatabaseMetadata databaseMetadata() {
+      return null;
+    }
+
+    @Override
+    public <R> void schedule(CommandBase<R> cmd, Completable<R> handler) {
+      handler.fail("not supported");
+    }
+  }
+
+  private Vertx vertx;
+  private SqlConnectionPool pool;
+  private final AtomicBoolean hookFails = new AtomicBoolean(true);
+  private final Exception hookFailure = new Exception("hook failure");
+
+  @Before
+  public void setUp() {
+    vertx = Vertx.vertx();
+    ConnectionFactory<SqlConnectOptions> factory = new ConnectionFactory<SqlConnectOptions>() {
+      @Override
+      public Future<Connection> connect(Context context, SqlConnectOptions options) {
+        return Future.succeededFuture(new StubConnection());
+      }
+      @Override
+      public void close(Completable<Void> completion) {
+        completion.succeed();
+      }
+    };
+    pool = new SqlConnectionPool(
+      () -> Future.succeededFuture(new SqlConnectOptions()),
+      factory,
+      null,
+      null,
+      conn -> hookFails.get() ? Future.failedFuture(hookFailure) : Future.succeededFuture(),
+      conn -> Future.succeededFuture(),
+      (VertxInternal) vertx,
+      0,
+      0,
+      1,
+      false,
+      -1,
+      0);
+  }
+
+  @After
+  public void tearDown(TestContext ctx) {
+    pool.close().onComplete(ctx.asyncAssertSuccess(v -> {
+      vertx.close().onComplete(ctx.asyncAssertSuccess());
+    }));
+  }
+
+  @Test
+  public void testAcquireFailsWithHookFailureAndReleasesTheSlot(TestContext ctx) {
+    Async async = ctx.async();
+    ContextInternal context = (ContextInternal) vertx.getOrCreateContext();
+    pool.acquire(context, 0, (conn, err) -> {
+      // the acquisition must report the hook failure, not null
+      ctx.assertEquals(hookFailure, err);
+      hookFails.set(false);
+      // the pool has a single slot: this acquisition succeeds only if the failed one was released
+      pool.acquire(context, 0, (conn2, err2) -> {
+        ctx.assertNull(err2);
+        ctx.assertNotNull(conn2);
+        async.complete();
+      });
+    });
+  }
+}