This report describes a case of hypotony maculopathy developing in a patient with GAPO syndrome following a trabeculectomy with mitomycin C (MMC). A 42-year-old man with a diagnosis of GAPO syndrome underwent a trabeculectomy with an MMC application of 0.4 mg/mL for 1 minute. Intraocular pressure was measured at 6 to 8 mmHg during the first weeks after the surgery. A fundus examination then revealed macular choroidal folds, retinal vascular tortuosity, and swelling in the optic nerve. At postoperative 1 month, additional suturing of a bleb was performed; however, the hypotony continued. Postoperative hypotony should be taken into account in patients with GAPO syndrome due to a defective fibrosis process following a trabeculectomy.Keywords: GAPO syndrome, hypotony maculopathy, mitomycin C, trabeculectomy.