We report a single case of masquerade glaucoma caused by increased episcleral venous pressure from adnexal lymphoma. The patient presented as a referral for unilateral glaucoma with intraocular pressures (IOPs) consistently >40 mm Hg (right eye). We present data conclusively demonstrating extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue in the involved eye, and provide an account of the treatment of the tumor with sustained regression and complete resolution of his elevated IOP. We conclude with a discussion of the proposed mechanism. This case serves as a reminder that unilateral open-angle glaucoma can be a sign of indolent ocular adnexal lymphoma. The case also provides a useful model for increased IOP with orbital lesions.