Optic neuritis (ON) may rarely mimic optic nerve tumor, index of suspicion should be kept high. A 34-year-old woman presented to a major academic institute with a history of right-sided ocular pain and progressive visual loss in the same eye. Her magnetic resonance imaging showed markedly thickened optic nerve; her workup for inflammatory pathology was negative; she was diagnosed as a case of optic nerve tumor and was planned for surgery. Patient for second opinion came to a tertiary care institute where on proper history taking and evaluation she was diagnosed and treated on the lines of ON and she improved. The diagnosis of ON is a clinical one, it may mimic optic nerve tumor in rare cases.