diff --git a/tests/nexus/test_1_2_BBR_TC_2.cpp b/tests/nexus/test_1_2_BBR_TC_2.cpp
index 2a94ca527..05744fee7 100644
--- a/tests/nexus/test_1_2_BBR_TC_2.cpp
+++ b/tests/nexus/test_1_2_BBR_TC_2.cpp
@@ -49,6 +49,11 @@ static constexpr uint32_t kAttachToRouterTime = 200 * 1000;
  */
 static constexpr uint32_t kStabilizationTime = 10 * 1000;
 
+/**
+ * Time to advance for leader failover and BBR promotion, in milliseconds.
+ */
+static constexpr uint32_t kLeaderFailoverTime = 400 * 1000;
+
 /**
  * Partition weight for Router_1 to ensure it becomes leader.
  */
@@ -357,7 +362,7 @@ void Test_1_2_BBR_TC_2(void)
      */
     Log("Step 14: BR_1 (DUT) becomes Leader and Primary BBR");
 
-    nexus.AdvanceTime(kAttachToRouterTime);
+    nexus.AdvanceTime(kLeaderFailoverTime); // Time for leader failover and BBR promotion (milliseconds)
 
     VerifyOrQuit(br1.Get<Mle::Mle>().IsLeader());
     VerifyOrQuit(br1.Get<BackboneRouter::Local>().IsPrimary());