Mature green tomatoes (Solanum lycopersicum ‘Neang Pich’) were exposed to 0, 3.1, 7.1, 10.5 and 13.6 kJ m-2 UV-C irradiation at 20°C. After treatment, tomatoes were stored in continuous air containing either <0.005 or 0.1 μL L-1 ethylene at 20°C and 100% RH for up to 11 days. The untreated fruit (0 kJ m-2 UV-C) ripened significantly faster than UV-C treatments in both storage conditions. All UV-C treatments followed by storage at either <0.005 and 0.1 μL L-1 ethylene had significantly slower ethylene production rates throughout the ripening period. There was no difference between treatments in fruit TSS, TA and, TSS/TA ratio. After storage, fruit treated with 10.5 and 13.6 kJ m-2 UV-C were significantly firmer than untreated fruits for both storage conditions. Overall, tomatoes stored at <0.005 μL L-1 ethylene were significantly firmer and had lower TSS/TA ratio than fruits stored at 0.1 μL L-1 ethylene. These results show that UV-C treatment delayed ripening of tomatoes in the presence of low level of ethylene during storage. In the absence of added ethylene, UV-C treatment resulted in firmer fruit with higher TSS and TSS/TA ratios. This new treatment could be used to extend the shelf-life of mature green tomatoes through the supply chain.