diff --git a/subsys/bluetooth/controller/ll_sw/ull_conn.c b/subsys/bluetooth/controller/ll_sw/ull_conn.c
index e3b747405e0..cdbe59514bb 100644
--- a/subsys/bluetooth/controller/ll_sw/ull_conn.c
+++ b/subsys/bluetooth/controller/ll_sw/ull_conn.c
@@ -6445,8 +6445,43 @@ static uint8_t cis_req_recv(struct ll_conn *conn, memq_link_t *link,
 	struct node_rx_conn_iso_req *conn_iso_req;
 	uint16_t cis_handle;
 	uint8_t err;
+	uint8_t phy;
 	void *node;
 
+	phy = req->c_phy;
+
+	/* Check reqested PHYs. Returning BT_HCI_ERR_INVALID_LL_PARAM shall invoke
+	 * sending of LL_REJECT_EXT_IND.
+	 */
+	for (uint8_t i = 0; i < 2; i++) {
+		/* Fail on multiple PHY specified */
+		if (util_ones_count_get(&phy, sizeof(phy)) > 1U) {
+			return BT_HCI_ERR_INVALID_LL_PARAM;
+		}
+
+		/* Fail on no PHY specified */
+		if (util_ones_count_get(&phy, sizeof(phy)) == 0U) {
+			return BT_HCI_ERR_INVALID_LL_PARAM;
+		}
+
+		/* Fail on unsupported PHY specified */
+		if (((phy & PHY_2M) &&
+		     !(conn->llcp_feature.features_conn & BIT64(BT_LE_FEAT_BIT_PHY_2M))) ||
+		    ((phy & PHY_CODED) &&
+		     !(conn->llcp_feature.features_conn & BIT64(BT_LE_FEAT_BIT_PHY_CODED)))) {
+			return BT_HCI_ERR_INVALID_LL_PARAM;
+		}
+
+		phy &= ~(PHY_1M|PHY_2M|PHY_CODED);
+
+		/* Fail on RFU bits specified */
+		if (util_ones_count_get(&phy, sizeof(phy))) {
+			return BT_HCI_ERR_INVALID_LL_PARAM;
+		}
+
+		phy = req->p_phy;
+	}
+
 	conn->llcp_cis.cig_id = req->cig_id;
 	conn->llcp_cis.cis_offset_min = sys_get_le24(req->cis_offset_min);
 	conn->llcp_cis.cis_offset_max = sys_get_le24(req->cis_offset_max);