Prostaglandin analogues have been reported to cause periorbital pigmentation. We report a case of open-angle glaucoma in which extensive facial skin pigmentation was noticed as an adverse effect of the use of latanoprost (Xalatan; Pfizer Inc., Puurs, Belgium). A 63-year-old woman with a 9-month history of primary open-angle glaucoma visited our facility. The glaucoma had been inadequately controlled by brimonidine 0.2% twice daily. The topical medication had been switched to latanoprost 0.005% 6 months prior to this visit in order to better control the intraocular pressure (IOP). Extensive facial skin pigmentation was noted by the ophthalmologist within 1 month. The latanoprost treatment was discontinued soon after the adverse effect was observed. The pigmentation became lighter and increasingly less noticeable within 3 months. Careful monitoring of the adverse effects of antiglaucoma medication is needed for patients with glaucoma. We report a rare case in which latanoprost treatment could have caused pigmentation of the entire facial skin. This condition should be monitored in the future by ophthalmologists to determine other existing cases.