End-to-end delay adaptation in conjunction with connected discontinuous reception (C-DRX) mode communication during cellular voice calls. A Voice over LTE (VoLTE) call may be established between a first wireless user equipment (UE) device and a second UE. End-to-end delay between real-time transport protocol (RTP) layers of the first UE and the second UE for the VoLTE call may be estimated. The end-to-end delay may be compared with one or more thresholds A C-DRX cycle length for the VoLTE call may be modified based on comparing the end-to-end delay with the one or more thresholds.