The aim of this study was to investigate the effects of ripasudil, a Rho-associated protein kinase (ROCK) inhibitor recently developed for glaucoma therapy in Japan, on intraocular pressure (IOP) and conjunctival scarring in a canine model of glaucoma surgery. Glaucoma surgery models were created in 10 eyes of five beagles. Immediately after surgery, one drop (50 μL) of 0.4% ripasudil hydrochloride hydrate solution (treated eyes) or phosphate saline alone (control eyes) was instilled twice daily for 4 weeks. IOPs and bleb features were assessed for 4 weeks, followed by histological evaluation. Proliferative cell nuclear antigen (PCNA)-positive cells and transforming growth factor (TGF)-β-positive cells were quantified. IOP was found to be significantly lower in the treated eyes than in the control eyes. The ratio of conjunctival area to scleral area was reduced in the treated eyes. In addition, the bleb score was higher, whereas the adhesion score and density of PCNA-positive and TGF-β-positive cells were lower in the treated eyes. Topical application of ripasudil maintained bleb formation and IOP reduction by suppressing cell proliferation. These results suggest that ripasudil might be useful for maintaining filtering blebs after glaucoma filtration surgery.