Gher farming is a unique fish farming systems in coastal region of Bangladesh that combines f reshwater prawn, fish, rice and vegetables. This study aims at examining the sy stem’s performance by examining economies of diversification and scale among these complementary enterprises and technical efficiency of the whole farm. The stochastic output distance function is used to measure economies of diversification , scale and technical efficiency based on the data obtained through direct interview of 452 gher based prawn fish farms. The finding indicates that there is an existence of significant technical inefficiency in gher farming, which implies that there may be opportunities expand gher outputs by eliminating technical inefficiency. Furthermore, there exist diversification economies in gher prawn farming, particularly in the prawn with other fish and with vegetable combination. Scale diseconomies (0.708) are also found in gher farming. The estimated technical efficiency level is 74 % suggesting that there is potential to recover a substantial amount of output (26 %) by reducing inefficiencies. Diversification among enterprises leads to significant efficiency gains. Moreover, farmers’ education, experience, access to credit and plot size positively impact efficiency. These results suggest that promoting diversification, especially prawn-rice combination, is benef icial for gher farming systems.