A method of failure event reporting for initial connection setup failure is proposed. In one embodiment, a UE first camps in RRC_IDLE mode in a cell served by a base station. The UE then detects a connection setup failure when performing a random access channel (RACH) procedure with the base station in an RRC connection attempt. The UE records a failure event report when the RACH procedure fails. Later, the UE transmits the failure event report to the network in RRC_CONNECTED mode. The failure event report comprises information that refers to the earlier RRC connection attempt. The failure event report also comprises available location information or available mobility measurements at the time the initial connection setup failure occurs. Based on the failure event report, the network can adopt corrective actions accordingly to mitigate the failure.