A case of Coats' syndrome presenting with acute secondary open-angle glaucoma is described. A 41-year-old woman presented with eye pain and an intraocular pressure of 50 mm Hg in the right eye. Numerous hyperrefringent yellow-white crystals were seen in the anterior chamber and in a recessed anterior chamber angle. Fundus examination revealed an inferior yellow exudative retinal detachment with retinal vascular abnormalities resembling Coats' disease. Following lensectomy, vitrectomy, retinal reattachment, and endolaser photocoagulation, the intraocular pressure stabilized within normal limits. Coats' syndrome may cause increased intraocular pressure by a secondary open-angle mechanism, even in phakic eyes. Removal of the lipid crystals and treatment of the anomalous vessels may be sufficient to control the intraocular pressure.