This study investigated the effects of O3 on growth, yields and physiological characteristics of Thai Jasmine rice cultivars. Rice was exposed to O3 for 7 h day−1 in a closed chamber for 113 days, beginning from seedling until harvest. O3 concentration in each chambers was controlled at 0 ppb, 50 ppb, 100 ppb, 150 ppb and at the ambient level. Effects of O3 on leaf area index (LAI) became obvious at maturity when LAI significantly decreased in the treatments under elevated O3 concentrations. Results in shoot biomass indicated that shoot length was more affected by O3 than shoot dry weight. Root length rather than dry weight was significantly reduced in all cultivars. The most severe damage of O3 was found in photosynthetic components, namely chlorophyll and carotenoid contents, and rate of net photosynthesis. Yield components were also strongly affected by O3. The highest reduction in filled seed per ear was found in the Pathumthani 1 cultivar by 78% when it was exposed to 150 ppb O3 compared to the control (0 ppb). Similarly, 100-grain weight was also reduced as much as 12.3% in this cultivar.