Abstract: A study was conducted to evaluate the impact of future climate change on the productivity of major cereal crop, rice at different time periods of 21st century (2020, 2050 and 2080). Future changes in temperatures and precipitation for the years 2020, 2050 and 2080 were acquired from HADCM3 model run outputs and integrated with the base year (2000) data for creating weather files to run INFOCROP model in order to predict the yield of the study crops under changing environment. The rice variety chosen for simulation was IR 36 and different CO2 concentration levels viz., 376 ppm, 414 ppm, 522 ppm, 682 ppm were used in the INFOCROP model at different time periods (2000, 2020, 2050 and 2080) for assessing the impacts on crop productivity as projected in the IPCC (2001) report. The crop growth and productivity simulated for the future climate using INFOCROP model indicated that the crop duration, days to anthesis, LAI and DMP of rice crop steadily decreased from 2000 to 2020, 2050 and 2080 due to increase in temperature under enriched CO2 levels. The magnitude of decrease from 2050 to 2080 is expected to be more than that of from 2000 to 2020 and 2020 to 2050. Similarly model recorded the less number of grains per square meter over years. Hence the study reveals prominent negative effects of future climate change on rice crop which shows the necessity to alter the management practices suitable to it.