diff --git a/include/zephyr/bluetooth/audio/cap.h b/include/zephyr/bluetooth/audio/cap.h
index f04c5c82814..3409e000d9c 100644
--- a/include/zephyr/bluetooth/audio/cap.h
+++ b/include/zephyr/bluetooth/audio/cap.h
@@ -346,7 +346,10 @@ int bt_cap_initiator_unregister_cb(const struct bt_cap_initiator_cb *cb);
  *
  * @param param Parameters to start the audio streams.
  *
- * @return 0 on success or negative error value on failure.
+ * @retval 0 on success
+ * @retval -EBUSY if a CAP procedure is already in progress
+ * @retval -EINVAL if any parameter is invalid
+ * @retval -EALREADY All streams are already in the streaming state
  */
 int bt_cap_initiator_unicast_audio_start(const struct bt_cap_unicast_audio_start_param *param);
 
diff --git a/subsys/bluetooth/audio/cap_initiator.c b/subsys/bluetooth/audio/cap_initiator.c
index e6a16c4bf5a..552bc724e11 100644
--- a/subsys/bluetooth/audio/cap_initiator.c
+++ b/subsys/bluetooth/audio/cap_initiator.c
@@ -26,6 +26,7 @@
 #include <zephyr/sys/check.h>
 #include <zephyr/sys/util.h>
 #include <zephyr/sys/util_macro.h>
+#include <sys/errno.h>
 
 #include "bap_endpoint.h"
 #include "cap_internal.h"
@@ -860,6 +861,8 @@ static int cap_initiator_unicast_audio_configure(
 
 int bt_cap_initiator_unicast_audio_start(const struct bt_cap_unicast_audio_start_param *param)
 {
+	bool all_streaming = true;
+
 	if (bt_cap_common_proc_is_active()) {
 		LOG_DBG("A CAP procedure is already in progress");
 
@@ -870,6 +873,20 @@ int bt_cap_initiator_unicast_audio_start(const struct bt_cap_unicast_audio_start
 		return -EINVAL;
 	}
 
+	for (size_t i = 0U; i < param->count; i++) {
+		const struct bt_bap_stream *bap_stream =
+			&param->stream_params[i].stream->bap_stream;
+
+		if (!stream_is_in_state(bap_stream, BT_BAP_EP_STATE_STREAMING)) {
+			all_streaming = false;
+		}
+	}
+
+	if (all_streaming) {
+		LOG_DBG("All streams are already in the streaming state");
+		return -EALREADY;
+	}
+
 	return cap_initiator_unicast_audio_configure(param);
 }
 
diff --git a/tests/bluetooth/audio/cap_initiator/src/test_unicast_start.c b/tests/bluetooth/audio/cap_initiator/src/test_unicast_start.c
index 9f73712f2f0..7ff7f2472ff 100644
--- a/tests/bluetooth/audio/cap_initiator/src/test_unicast_start.c
+++ b/tests/bluetooth/audio/cap_initiator/src/test_unicast_start.c
@@ -500,3 +500,40 @@ static ZTEST_F(cap_initiator_test_unicast_start, test_initiator_unicast_start_st
 			      "[%zu]: Stream %p unexpected state: %d", i, bap_stream, state);
 	}
 }
+
+static ZTEST_F(cap_initiator_test_unicast_start, test_initiator_unicast_start_state_streaming)
+{
+	struct bt_cap_unicast_audio_start_stream_param
+		stream_params[CONFIG_BT_BAP_UNICAST_CLIENT_GROUP_STREAM_COUNT] = {0};
+	const struct bt_cap_unicast_audio_start_param param = {
+		.type = BT_CAP_SET_TYPE_AD_HOC,
+		.count = ARRAY_SIZE(stream_params),
+		.stream_params = stream_params,
+	};
+	int err;
+
+	for (size_t i = 0U; i < ARRAY_SIZE(stream_params); i++) {
+		stream_params[i].stream = &fixture->cap_streams[i];
+		stream_params[i].codec_cfg = &fixture->preset.codec_cfg;
+		stream_params[i].member.member = &fixture->conns[i % ARRAY_SIZE(fixture->conns)];
+		stream_params[i].ep = &fixture->eps[i];
+
+		test_unicast_set_state(stream_params[i].stream, stream_params[i].member.member,
+				       stream_params[i].ep, &fixture->preset,
+				       BT_BAP_EP_STATE_STREAMING);
+	}
+
+	err = bt_cap_initiator_unicast_audio_start(&param);
+	zassert_equal(err, -EALREADY, "Unexpected return value %d", err);
+
+	zexpect_call_count("bt_cap_initiator_cb.unicast_start_complete_cb", 0,
+			   mock_cap_initiator_unicast_start_complete_cb_fake.call_count);
+
+	for (size_t i = 0U; i < ARRAY_SIZE(stream_params); i++) {
+		const struct bt_bap_stream *bap_stream = &fixture->cap_streams[i].bap_stream;
+		const enum bt_bap_ep_state state = bap_stream->ep->status.state;
+
+		zassert_equal(state, BT_BAP_EP_STATE_STREAMING,
+			      "[%zu]: Stream %p unexpected state: %d", i, bap_stream, state);
+	}
+}