SIGNIFICANCE Ophthalmic manifestations of non-Hodgkin lymphoma are rare, and the diagnosis can be delayed because of nonspecific symptoms and a tendency to mimic the appearance of other ocular diseases. Suspicious presentations will require confirmation of the lymphoma through surgical biopsy. PURPOSE The purpose of this study was to present an isolated conjunctival non-Hodgkin marginal zone lymphoma without systemic involvement, which was successfully managed with external beam radiation. CASE REPORT A 49-year-old man reported a red, temporal bulbar conjunctival growth on the left eye for several weeks, which was initially treated as a nodular episcleritis. When the condition did not resolve, a subsequent biopsy diagnosed a low-grade non-Hodgkin marginal zone lymphoma; further testing found no systemic involvement. No intraocular involvement was noted, and B-scan ultrasound and magnetic resonance imaging did not demonstrate any uveal or orbital extension. A trial of doxycycline did not lead to regression, and the isolated lesion was observed. Because of possible slow growth, the lesion was eventually treated with external beam radiation, which resulted in significant tumor regression. Four years after the radiotherapy, the tumor has not recurred, and there has been no systemic involvement. CONCLUSIONS This case of a low-grade extranodal marginal zone lymphoma on the temporal conjunctiva represents a less common variation of the classic fornix-based presentation. It is not unusual for conjunctival lymphomas to masquerade as another clinical entity, sometimes making the initial diagnosis challenging. If a patient does not respond as expected to conventional therapy, a biopsy to rule out malignancy should be considered.