diff --git a/subsys/bluetooth/audio/bap_broadcast_assistant.c b/subsys/bluetooth/audio/bap_broadcast_assistant.c
index 36c8c46171fce4..07f83bd7c13115 100644
--- a/subsys/bluetooth/audio/bap_broadcast_assistant.c
+++ b/subsys/bluetooth/audio/bap_broadcast_assistant.c
@@ -768,7 +768,8 @@ int bt_bap_broadcast_assistant_add_src(struct bt_conn *conn,
 
 		subgroup = net_buf_simple_add(&cp_buf, subgroup_size);
 
-		subgroup->bis_sync = param->subgroups[i].bis_sync;
+		/* The BIS Index bitfield to be sent must use BIT(0) for BIS Index 1 */
+		subgroup->bis_sync = param->subgroups[i].bis_sync >> 1;
 
 		CHECKIF(param->pa_sync == 0 && subgroup->bis_sync != 0) {
 			LOG_DBG("Only syncing to BIS is not allowed");
@@ -860,7 +861,8 @@ int bt_bap_broadcast_assistant_mod_src(struct bt_conn *conn,
 		}
 		subgroup = net_buf_simple_add(&cp_buf, subgroup_size);
 
-		subgroup->bis_sync = param->subgroups[i].bis_sync;
+		/* The BIS Index bitfield to be sent must use BIT(0) for BIS Index 1 */
+		subgroup->bis_sync = param->subgroups[i].bis_sync >> 1;
 
 		CHECKIF(param->pa_sync == 0 && subgroup->bis_sync != 0) {
 			LOG_DBG("Only syncing to BIS is not allowed");
diff --git a/subsys/bluetooth/audio/bap_scan_delegator.c b/subsys/bluetooth/audio/bap_scan_delegator.c
index 3e31408b450c97..296a8f47f65d09 100644
--- a/subsys/bluetooth/audio/bap_scan_delegator.c
+++ b/subsys/bluetooth/audio/bap_scan_delegator.c
@@ -514,6 +514,10 @@ static int scan_delegator_add_source(struct bt_conn *conn,
 		}
 
 		internal_state->requested_bis_sync[i] = net_buf_simple_pull_le32(buf);
+		if (internal_state->requested_bis_sync[i] != BT_BAP_BIS_SYNC_NO_PREF) {
+			/* Received BIS Index bitfield uses BIT(0) for BIS Index 1 */
+			internal_state->requested_bis_sync[i] <<= 1;
+		}
 
 		if (internal_state->requested_bis_sync[i] &&
 		    pa_sync == BT_BAP_BASS_PA_REQ_NO_SYNC) {
@@ -670,6 +674,11 @@ static int scan_delegator_mod_src(struct bt_conn *conn,
 		old_bis_sync_req = internal_state->requested_bis_sync[i];
 
 		internal_state->requested_bis_sync[i] = net_buf_simple_pull_le32(buf);
+		if (internal_state->requested_bis_sync[i] != BT_BAP_BIS_SYNC_NO_PREF) {
+			/* Received BIS Index bitfield uses BIT(0) for BIS Index 1 */
+			internal_state->requested_bis_sync[i] <<= 1;
+		}
+
 		if (internal_state->requested_bis_sync[i] &&
 		    pa_sync == BT_BAP_BASS_PA_REQ_NO_SYNC) {
 			LOG_DBG("Cannot sync to BIS without PA");