In this paper, a new cooperation scenario and relay selection algorithm is proposed for wireless networks using cooperative spatial modulation. The proposed method is based on the selection of best relay for spatial modulation. In addition, spatial modulation was implemented by selecting 4 best relays from 4 different relay groups, resulting improved performance. The average symbol error probabilities are calculated to test the transmission performance of the proposed method using computer simulations. Results show that the proposed cooperative spatial modulation scheme improves the system performance.