Feasibility replacing dietary soybean meal (SBM) for fishmeal was assessed on Portunus pelagicus. 20% SBM diets led to best growth, despite lower trypsin activity. Hepatopancreatic damage and reduced glycogen was found at 80 and 100% SBM. SBM at 40% can be used in the diets of P. pelagicus without affecting survival or growth.