diff --git a/include/bluetooth/iso.h b/include/bluetooth/iso.h
index 84fc7015ad7..705e99fb66b 100644
--- a/include/bluetooth/iso.h
+++ b/include/bluetooth/iso.h
@@ -313,7 +313,12 @@ struct bt_iso_big_sync_param {
 	 */
 	uint8_t num_bis;
 
-	/** Bitfield of the BISes to sync to */
+	/** Bitfield of the BISes to sync to
+	 *
+	 *  The BIS indexes start from 0x01, so the lowest allowed bit is
+	 *  BIT(1) that represents index 0x01. To synchronize to e.g. BIS
+	 *  indexes 0x01 and 0x02, the bitfield value should be BIT(1) | BIT(2).
+	 */
 	uint32_t bis_bitfield;
 
 	/** @brief Maximum subevents
diff --git a/samples/bluetooth/iso_broadcast_benchmark/src/receiver.c b/samples/bluetooth/iso_broadcast_benchmark/src/receiver.c
index 0638f0de0a2..998d688017a 100644
--- a/samples/bluetooth/iso_broadcast_benchmark/src/receiver.c
+++ b/samples/bluetooth/iso_broadcast_benchmark/src/receiver.c
@@ -363,7 +363,8 @@ static int create_big_sync(struct bt_iso_big **big, struct bt_le_per_adv_sync *s
 	sync_timeout_ms = iso_interval_ms * ISO_RETRY_COUNT;
 	big_sync_param.sync_timeout = CLAMP(sync_timeout_ms / 10, 0x000A, 0x4000); /* 10 ms units */
 	big_sync_param.num_bis = bis_count;
-	for (int i = 0; i < big_sync_param.num_bis; i++) {
+	/* BIS indexes start from 0x01, so add one to `i` */
+	for (int i = 1; i <= big_sync_param.num_bis; i++) {
 		big_sync_param.bis_bitfield |= BIT(i);
 	}
 
diff --git a/samples/bluetooth/iso_receive/src/main.c b/samples/bluetooth/iso_receive/src/main.c
index a65cb6848d5..e5f8211131d 100644
--- a/samples/bluetooth/iso_receive/src/main.c
+++ b/samples/bluetooth/iso_receive/src/main.c
@@ -263,7 +263,7 @@ static struct bt_iso_chan *bis[BIS_ISO_CHAN_COUNT] = { &bis_iso_chan };
 static struct bt_iso_big_sync_param big_sync_param = {
 	.bis_channels = bis,
 	.num_bis = BIS_ISO_CHAN_COUNT,
-	.bis_bitfield = (BIT(BIS_ISO_CHAN_COUNT) - 1),
+	.bis_bitfield = (BIT_MASK(BIS_ISO_CHAN_COUNT) << 1),
 	.mse = 1,
 	.sync_timeout = 100, /* in 10 ms units */
 };
diff --git a/subsys/bluetooth/host/iso.c b/subsys/bluetooth/host/iso.c
index 67ee0dd18db..8db970123c8 100644
--- a/subsys/bluetooth/host/iso.c
+++ b/subsys/bluetooth/host/iso.c
@@ -1850,13 +1850,13 @@ static int hci_le_big_create_sync(const struct bt_le_per_adv_sync *sync, struct
 	req->sync_timeout = sys_cpu_to_le16(param->sync_timeout);
 	req->num_bis = big->num_bis;
 	/* Transform from bitfield to array */
-	for (int i = 0; i < BT_ISO_MAX_GROUP_ISO_COUNT; i++) {
+	for (int i = 1; i <= BT_ISO_MAX_GROUP_ISO_COUNT; i++) {
 		if (param->bis_bitfield & BIT(i)) {
 			if (bit_idx == big->num_bis) {
 				BT_DBG("BIG cannot contain %u BISes", bit_idx + 1);
 				return -EINVAL;
 			}
-			req->bis[bit_idx++] = i + 1; /* indices start from 1 */
+			req->bis[bit_idx++] = i;
 		}
 	}
 
@@ -1894,7 +1894,7 @@ int bt_iso_big_sync(struct bt_le_per_adv_sync *sync, struct bt_iso_big_sync_para
 		return -EINVAL;
 	}
 
-	CHECKIF(!param->bis_bitfield) {
+	CHECKIF(param->bis_bitfield <= BIT(0)) {
 		BT_DBG("Invalid BIS bitfield 0x%08x", param->bis_bitfield);
 		return -EINVAL;
 	}