Diabetic retinopathy (DR) is a major cause of blindness, and there is a lack of effective treatment at present. Rho-associated coiled-coil containing serine/threonine protein kinases (ROCKs) have recently been suggested as potential targets for the DR treatment. We herein report the discovery of 4H-chromen-4-one derivatives as a new class of ROCK inhibitors. Structure-activity relationship analyses led to the identification of the most active compound, 4-(dimethylamino)-N-(3-{2-[(4-oxo-4H-chromen-7-yl)oxy]acetamido}phenyl) (12j). This compound showed excellent kinase selectivity for ROCK I and ROCK II against 387 other kinases. In retinal explants, compound 12j protected retinal neurons from high glucose-induced oxidative stress and apoptosis-mediated cell death. Furthermore, 12j administration suppressed the improper proliferation of Müller cells and promoted the regression of vascular vessels in retinal explants cultured in a high glucose microenvironment. Collectively, our data suggest that 12j could be a potential lead compound for the treatment of DR, hence deserving further in-depth studies.