Sorbitol is the primary photosynthetic end product in the leaves of many tree fruit species in the Rosaceae family, but its physiological role remains unclear. In this study, we determined the effect of decreased sorbitol synthesis on the antioxidant system that scavenges reactive oxygen species (ROS) in apple leaves. Sorbitol synthesis was decreased in apple leaves by antisense inhibition of aldose-6-phosphate reductase activity. Dehydroascorbate reductase (DHAR), glutathione reductase, and catalase (CAT) activities increased in the leaves of the transgenic plants with decreased sorbitol synthesis, whereas superoxide dismutase, ascorbate peroxidase, NADH dependent and NADPH dependent monodehydroascorbate reductase activity did not show significant changes. Ascorbate and glutathione concentrations were higher in leaves of the transgenic plants compared with the control. The effect of decreased sorbitol synthesis on the antioxidant enzyme activity was dependent on leaf developmental stages. Larger changes in the enzyme activities of CAT, DHAR, and GR were observed in the old leaves than in the young leaves. These results suggest that sorbitol may play a role in ROS scavenging in apple leaves.