Orthogonal frequency division multiplexing based cooperative system using Alamouti space–time block coding at relay node represents an alternative solution to achieve better connectivity and significant enhancement to the data rate in wireless fading channels. But, these advantages cannot be achieved without an efficient estimation of the channels which becomes more challenging for cooperative communications. This paper addresses the joint channel estimation and data detection for cooperative communication systems. Indeed, equispaced pilot symbols are used by maximum likelihood (ML) algorithm to derive channels estimator, and then equalizers are calculated and applied to improve receiver data detection. The main contribution of our work is the development of the ML estimator, the corresponding Cramer–Rao lower bound, mean square error, signal to interference plus noise ratio, outage probability, bit error probability and the use of simulations to demonstrate the superior performances of the proposed methods.