Ahmed glaucoma valve implant appears to be a relatively useful drainage device in eyes with glaucoma secondary to Sturge-Weber syndrome (SWS). However, early postoperative choroidal and exudative retinal detachment may occur from a rapid expansion of the choroidal hemangioma with effusion of fluid into the suprachoroidal and subretinal spaces. We report the case of a ten-year-old boy who had SWS with choroidal haemangioma and secondary glaucoma. He had Ahmed glaucoma valve implantation on account of the secondary glaucoma which had been refractory to both conventional medical and surgical managements. He developed choroidal and exudative retinal detachment postoperatively. However, he responded to conservative treatment and further surgical management was not required. Ahmed glaucoma valve in the treatment of glaucoma secondary to SWS is useful, but the risk of choroidal effusion with exudative retinal detachment is still present. Surgeons should be alert to this likely complication and be prepared for prompt management.