In this study, a new energy-efficient hybrid opportunistic cooperative (HOC) transmission protocol is proposed for single-carrier frequency division multiple access (SC-FDMA)-based cooperative networks. The author considers a single source–destination pair and multiple relays network. The proposed protocol improves the energy efficiency of SC-FDMA-based networks by selecting the most energy-efficient cooperative transmission protocol from a set of available protocols according to the current channel state information. The protocols considered in the development of the HOC protocol are amplify-and-forward, decode-and-forward, compress-and-forward and estimate-and-forward. Computer simulation is done over four different scenarios of channel conditions. The obtained results show that the proposed HOC protocol significantly improves the delay-limited capacity and minimises the outage probability of SC-FDMA-based cooperative networks. The results also show that the minimum required average total power in the proposed HOC protocol is less than that of opportunistic decode-and-forward by 0.55 dB.