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The study was conducted in three major rice producing areas to assess the probable impact of climate change in Philippine rice production. Climate change scenarios were devised using general circulation models (GCMs) from ratios of climate variables (temperature, precipitation, and solar radiation) in the doubled CO2 runs to the current climate variables applied to observed weather data for each site.The GCMs used were the Goddard Institute for Space Studies (GISS), the Geophysical Fluid Dynamics Laboratory (GFDL), and the United Kingdom Meteorological Office (UKMO). The CERES-Rice IRSNAT Crop Model was modified to simulate the changes in photosynthesis and evapotranspiration caused by increases in atmospheric CO2. Sensitivity study was performed using step increases in temperature of + 2°C and +4°C combined with step changes in precipitation of +20% and -20%.Using the mean yield from three sites, results show that under scenario of climate change alone (330ppm of CO2), an average reduction in rice baseline yield of 22% will be experienced in the Philippines. However, under climate change with physiological CO2 effects (555ppm of CO2), an increase in baseline yield (at 330ppm level of CO2) of only 1% will a obtained. Increasing only the temperature by 2°C without any change in precipitation at 330ppm CO2 level will correspond to 21% reduction in yield. Further increase in temperature of 4°C will reduce the baseline yield by 39%. Changes in precipitation of -20% and +20% did not significantly affect the rice yields. Considering, however, the physiological effects of CO2 for sensitivity analysis, rice yields increased by 35% (+0°C), 42% (+2°C), and 58% (+4°C).Overall, results indicate a wide variation of regional responses to climate change. The Southern part seemed to be more vulnerable to climate change than the Northern Philippines.