Cellular Vehicle-to-everything (V2X) becomes one of the most significant techniques in the 5G standard. It uses the PC5 sidelink interface to enable direct communications between the vehicle and everything, e.g., neighboring vehicles, the infrastructure, and pedestrians. To facilitate ultra-reliable low-latency communication (URLLC) in high dense vehicular networks, this paper studies the feasibility of non-orthogonal multiple access (NOMA) in C-V2X to improve the spectral efficiency. According to the orthogonal multiple access (OMA) based PHY layer as specified in the PC5 sidelink interface, we propose two NOMA receivers based on two techniques: successive interference cancellation (SIC) and joint decoding (JD). It is demonstrated that the two receivers can be easily implemented on current C-V2X communications with minor modifications. Simulation results show that the two NOMA approaches can reduce the block error rate (BLER) by up to 93.6% as compared with the conventional OMA approach. In general, JD receiver provides better BLER performance at the cost of higher computational complexity as compared to the SIC receiver.