Global climate change is among the most important agricultural and food security challenges. Study was conducted to investigate the effect of climate change on potential yield and water productivity of forage maize in Iran. Two scenarios of RCP4.5 and RCP8.5 was used to predict the future climate (2050s) and climate data of 2001-2015 were used as the base period. Potential yield was estimated using SSM-iCrop2 model according to the GYGA protocol and the climate changes for both scenarios were applied in the model. The results showed that the climate change will not have a considerable effect on forage maize yield compared to the current conditions (85.6 ton ha-1) and will only lead to an increase of 0.9 and 1.6 percent in on both scenarios. This may be attributed to maize being a C4 plant and thus, non-effectiveness of CO2 increase on its growth. Also, the temperature will remain in optimum range for maize in most of the main regions for forage maize cultivation areas in Iran. Water productivity in both scenarios will increase by 0.4 and 1.6 percent compared with the current conditions (10.4 kg m-3) which may be due to increase CO2 concentration and more closure of stomata. Also, improved water productivity in forage maize may be attributed to increase yield potential due to the fact that no considerable changes were observed in terms of the required water, evapotranspiration and irrigation times.