In vehicular ad hoc networks (VANETs), mobility among vehicles can result in rapid topology changes with frequent link breakage and unstable communications, which cause collision and packet loss. Conversely, cooperative transmission can improve communication reliability and can enhance communication rate with lower delay by alleviating wireless channel impairments caused by mobility in VANETs. In this study, a novel reliable and efficient cooperative medium access control protocol for VANETs (RECV-MAC) is proposed. Since a random access mechanism is suitable and efficient because of the dynamic and open nature of VANETs, authors used the random access approach, i.e. carrier sense multiple access with collision avoidance, which is used by IEEE 802.11p. The RECV-MAC protocol is compatible with IEEE 802.11p. New control messages are introduced to support cooperative communication. The mechanism is defined to choose suitable transmission mode as well as to select optimal helper. To investigate the performance of RECV-MAC protocol, Markov chain model-based analytical analysis is provided. The RECV-MAC protocol is validated by numerical results which demonstrate that RECV-MAC protocol improves the performance with higher throughput, enhances the reliability of communication by decreasing packet dropping rate (PDR), and decreases delay, in particular, satisfies the delay constraint of 100ms for sm.