In summary, different combinations of LI and NT induce differential growth responses of tomato seedlings, and the promotion induced by increasing LI was limited by higher NT. The responsive mechanisms of tomato plants to higher NT varied with LI levels. At LH level, higher NT inhibited tomato growth via reducing the leaf area, altering the Chl a/b and chloroplast shape, regulating excitation energy utilization and distribution, as well as carbon metabolism; while, in addition to some of the above reasons, the reduced antioxidant capacities were also probably responsible for growth constraints caused by higher NT at LM level. Whereas, elevated NT had a growth compensation for tomato seedlings under the lowest LI, via increasing stomatal length, pigments, free amino acid and AsA contents to improve physiological performance and light energy utilization under lower light. Comprehensive analysis showed that higher LI plus lower NT would be an effective strategy to improve tomato growth, while lower LI plus higher NT might be worth considering as a strategy for tomato production in hot season in view of energy consumption cost in a controlled environment.