Diabetic cataracts can occur at an early age, causing visual impairment or blindness. The detailed molecular mechanisms of diabetic cataract formation remain incompletely understood, and there is no well-documented prophylactic agent. Galactose-fed rats and ex vivo treatment of lenses with galactose are used as models of diabetic cataract. To assess the role of histone acetyltransferases, we conducted cataract prevention screening with known histone acetyltransferase (HAT) inhibitors. Ex vivo treatment with a HAT inhibitor strongly inhibited the formation of lens turbidity in high-galactose conditions, while addition of a histone deacetylase (HDAC) inhibitor aggravated turbidity. We conducted a microarray to identify genes differentially regulated by HATs and HDACs, leading to discovery of a novel cataract causative factor, Plk3. Plk3 mRNA levels correlated with the degree of turbidity, and Plk3 inhibition alleviated galactose-induced cataract formation. These findings indicate that epigenetically controlled Plk3 influences cataract formation. Our results demonstrate a novel approach for prevention of diabetic cataract using HAT and Plk3 inhibitors.