CO₂ fertilization has been widely used in greenhouse cultivation of tomato (Solanum lycopersicum) to enhance fruit yield; its effects on fruit quality remain largely elusive yet, particularly in combination with reduced irrigation regimes. To explore the response of tomato to the CO₂ fertilization under reduced irrigation, tomato (cv. Zhou Si Dun) plants were grown under ambient CO₂ (a[CO₂], 400 ppm) and elevated CO₂ (e[CO₂], 800 ppm) environment, respectively and subjected to three irrigation levels since anthesis: I1 (irrigated to 90–95 % water holding capacity of the mixture in the pot, WHC), I2 (irrigated to 70–75 % WHC) and I3 (irrigated to 50–55 % WHC). The results showed that fruit yield was significantly higher in plants with I1 than those with I3. Moreover, the e[CO₂] enhanced the number of fruit and decreased the percentage of small fruit (< 70 g), resulting in higher fruit yield as compared to a[CO₂]. Leaf area (LA), fruit dry weight (FDW), water use efficiency (WUE), as well as harvest index (HI) were increased under e[CO₂], whereas irrigation regime had no influence on FDW, WUE or HI. Both reduced irrigation and e[CO₂] increased total soluble solid, vitamin C and lycopene content, while decreased nitrate content in fruit. The results of PCA (Principal Component Analysis) indicated that there was a significant improvement in the comprehensive performance of plants with reduced irrigation at e[CO₂] environment. It can be concluded that reduced irrigation, combined with CO₂ fertilization, could be a promising strategy to enhance fruit quality in greenhouse tomato production under water-limited conditions.