In this study, Resource Allocation and Joint Mode Selection for Device-to-Device Communications (D2D) has been modelled using the cuckoo search algorithm (CSA). The implementation is made for equal power control and constraints ensuring that the existing sub-channels are used efficiently and optimally. Simultaneous access to radio resources in a coexistence scenario through D2D technology with optimal mode selection is considered. Initially, the problem formulation for resource allocation is written, then, a cuckoo search optimized solution for optimal resource allocation and mode selection in uplink cellular communications has been proposed and the same has been evaluated using throughput analysis.