diff --git a/src/core/radio/ble_secure.cpp b/src/core/radio/ble_secure.cpp
index ba66ed64b..3186f9509 100644
--- a/src/core/radio/ble_secure.cpp
+++ b/src/core/radio/ble_secure.cpp
@@ -196,10 +196,19 @@ Error BleSecure::NotifyAdvertisementChanged(void)
     uint16_t advertisementLen  = 0;
     uint8_t *advertisementData = nullptr;
 
-    VerifyOrExit(mBleState == kAdvertising);
+    VerifyOrExit(mBleState != kStopped);
     SuccessOrExit(error = otPlatBleGetAdvertisementBuffer(&GetInstance(), &advertisementData));
     SuccessOrExit(error = Get<MeshCoP::TcatAgent>().GetAdvertisementData(advertisementLen, advertisementData));
-    SuccessOrExit(error = otPlatBleGapAdvUpdateData(&GetInstance(), advertisementData, advertisementLen));
+
+    if (mBleState == kAdvertising)
+    {
+        SuccessOrExit(error = otPlatBleGapAdvUpdateData(&GetInstance(), advertisementData, advertisementLen));
+    }
+    else
+    {
+        // Any other state: update buffered data for when advertising resumes.
+        SuccessOrExit(error = otPlatBleGapAdvSetData(&GetInstance(), advertisementData, advertisementLen));
+    }
 
 exit:
     return error;
diff --git a/tests/scripts/expect/cli-tcat-decommission.exp b/tests/scripts/expect/cli-tcat-decommission.exp
index cfd5e589c..3825dac3c 100755
--- a/tests/scripts/expect/cli-tcat-decommission.exp
+++ b/tests/scripts/expect/cli-tcat-decommission.exp
@@ -53,6 +53,9 @@ send "thread start\n"
 expect_line "\tTYPE:\tRESPONSE_W_STATUS"
 expect_line "\tVALUE:\t0x00"
 
+send "disconnect\n"
+expect_line "Done"
+
 dispose_tcat_client 1
 
 switch_node 1
diff --git a/tests/unit/test_platform.cpp b/tests/unit/test_platform.cpp
index 621dd0f81..d29e3748d 100644
--- a/tests/unit/test_platform.cpp
+++ b/tests/unit/test_platform.cpp
@@ -801,6 +801,10 @@ OT_TOOL_WEAK otPlatMcuPowerState otPlatGetMcuPowerState(otInstance *aInstance) {
 OT_TOOL_WEAK otError otPlatSetMcuPowerState(otInstance *aInstance, otPlatMcuPowerState aState) { return OT_ERROR_NONE; }
 #endif // OPENTHREAD_CONFIG_NCP_ENABLE_MCU_POWER_STATE_CONTROL
 #ifdef OPENTHREAD_CONFIG_BLE_TCAT_ENABLE
+
+uint8_t  sPlatBleLastAdvSetData[OT_TCAT_ADVERTISEMENT_MAX_LEN];
+uint16_t sPlatBleLastAdvSetDataLen = 0;
+
 otError otPlatBleEnable(otInstance *aInstance)
 {
     OT_UNUSED_VARIABLE(aInstance);
@@ -875,17 +879,19 @@ bool otPlatBleSupportsMultiRadio(otInstance *aInstance)
 otError otPlatBleGapAdvSetData(otInstance *aInstance, uint8_t *aAdvertisementData, uint16_t aAdvertisementLen)
 {
     OT_UNUSED_VARIABLE(aInstance);
-    OT_UNUSED_VARIABLE(aAdvertisementData);
-    OT_UNUSED_VARIABLE(aAdvertisementLen);
+    if (aAdvertisementData == nullptr || aAdvertisementLen > OT_TCAT_ADVERTISEMENT_MAX_LEN)
+    {
+        return OT_ERROR_INVALID_ARGS;
+    }
+    memcpy(sPlatBleLastAdvSetData, aAdvertisementData, aAdvertisementLen);
+    sPlatBleLastAdvSetDataLen = aAdvertisementLen;
+
     return OT_ERROR_NONE;
 }
 
 otError otPlatBleGapAdvUpdateData(otInstance *aInstance, uint8_t *aAdvertisementData, uint16_t aAdvertisementLen)
 {
-    OT_UNUSED_VARIABLE(aInstance);
-    OT_UNUSED_VARIABLE(aAdvertisementData);
-    OT_UNUSED_VARIABLE(aAdvertisementLen);
-    return OT_ERROR_NONE;
+    return otPlatBleGapAdvSetData(aInstance, aAdvertisementData, aAdvertisementLen);
 }
 
 #endif // OPENTHREAD_CONFIG_BLE_TCAT_ENABLE
diff --git a/tests/unit/test_platform.h b/tests/unit/test_platform.h
index 4eedd4edc..87904c214 100644
--- a/tests/unit/test_platform.h
+++ b/tests/unit/test_platform.h
@@ -57,4 +57,16 @@ ot::Instance *testInitAdditionalInstance(uint8_t id);
 #endif
 void testFreeInstance(otInstance *aInstance);
 
+#if OPENTHREAD_CONFIG_BLE_TCAT_ENABLE
+#include <openthread/tcat.h>
+#ifdef __cplusplus
+extern "C" {
+#endif
+extern uint8_t  sPlatBleLastAdvSetData[OT_TCAT_ADVERTISEMENT_MAX_LEN];
+extern uint16_t sPlatBleLastAdvSetDataLen;
+#ifdef __cplusplus
+}
+#endif
+#endif
+
 #endif // OT_UNIT_TEST_PLATFORM_H_
diff --git a/tests/unit/test_tcat.cpp b/tests/unit/test_tcat.cpp
index 2c4acfd56..a6f8a7e16 100644
--- a/tests/unit/test_tcat.cpp
+++ b/tests/unit/test_tcat.cpp
@@ -36,6 +36,7 @@
 #include <openthread/ble_secure.h>
 
 #include "cli/cli_dataset.hpp"
+#include "radio/ble_secure.hpp"
 
 #define OT_TCAT_X509_CERT                                                \
     "-----BEGIN CERTIFICATE-----\n"                                      \
@@ -267,6 +268,8 @@ static Instance *TestInitInstanceTcat(void)
     memcpy(&sCommExtPanId, &kExtPanId, sizeof(sCommExtPanId));
     memcpy(&sCommAuth, &kCommCert1AuthField, sizeof(sCommAuth));
     memcpy(&sDeviceAuth, &kDeviceCert1AuthField, sizeof(sDeviceAuth));
+    sPlatBleLastAdvSetDataLen = 0;
+    memset(sPlatBleLastAdvSetData, 0, OT_TCAT_ADVERTISEMENT_MAX_LEN);
 
     return instance;
 }
@@ -336,6 +339,46 @@ void TestTcatConnectionAndCertAttributes(void)
     testFreeInstance(instance);
 }
 
+void TestTcatAdvertisementUpdates(void)
+{
+    TestBleSecure ble;
+    Instance     *instance = TestInitInstanceTcat();
+    uint8_t       advDataSnapshot[OT_TCAT_ADVERTISEMENT_MAX_LEN];
+    uint16_t      advDataSnapshotLen;
+
+    VerifyOrQuit(sPlatBleLastAdvSetDataLen == 0, "Adv data should be unset before BleSecure start");
+
+    SuccessOrQuit(otBleSecureStart(instance, HandleBleSecureConnect, nullptr, true, &ble));
+    SuccessOrQuit(otBleSecureTcatStart(instance, nullptr));
+
+    VerifyOrQuit(sPlatBleLastAdvSetDataLen > 0, "Adv data should be set after BleSecure start");
+    advDataSnapshotLen = sPlatBleLastAdvSetDataLen;
+    memcpy(advDataSnapshot, sPlatBleLastAdvSetData, advDataSnapshotLen);
+
+    otPlatBleGapOnConnected(instance, kConnectionId);
+    SuccessOrQuit(otBleSecureConnect(instance));
+
+    // BLE connect and initiating TLS does not change the adv data.
+    VerifyOrQuit(sPlatBleLastAdvSetDataLen == advDataSnapshotLen &&
+                     memcmp(sPlatBleLastAdvSetData, advDataSnapshot, advDataSnapshotLen) == 0,
+                 "Adv data changed unexpectedly after BLE connect");
+    advDataSnapshotLen = sPlatBleLastAdvSetDataLen;
+    memcpy(advDataSnapshot, sPlatBleLastAdvSetData, advDataSnapshotLen);
+
+    // Commissioner sets dataset, then disconnects
+    instance->Get<ActiveDatasetManager>().SaveLocal(sPartialDataset);
+    otBleSecureDisconnect(instance);
+
+    // Adv is changed due to the partial dataset now being advertised in the S flag.
+    VerifyOrQuit(sPlatBleLastAdvSetDataLen == advDataSnapshotLen, "Adv data length changed unexpectedly");
+    VerifyOrQuit(memcmp(sPlatBleLastAdvSetData, advDataSnapshot, advDataSnapshotLen) != 0,
+                 "Adv data did not change after disconnect, which it should due to S flag");
+
+    otBleSecureStop(instance);
+
+    testFreeInstance(instance);
+}
+
 class UnitTester
 {
 private:
@@ -834,6 +877,7 @@ int main(void)
     ot::MeshCoP::UnitTester::TestTcatCommissioner1AuthWithDeviceRequirements();
     ot::MeshCoP::UnitTester::TestTcatCommissioner2AuthWithDeviceRequirements();
     ot::MeshCoP::UnitTester::TestTcatCommissioner4AuthWithExistingPartialDataset();
+    ot::MeshCoP::TestTcatAdvertisementUpdates();
     printf("All tests passed\n");
 #else
     printf("TCAT feature is not enabled\n");