Lyme optic neuritis (ON) is a rare disease and only a few cases have been reported. We describe two cases of isolated Lyme ON, one with recurrence 9 months after the appearance of initial symptoms. Diagnosis criteria for multiple sclerosis and neuromyelitis optica were not met. The etiological diagnosis was based on European case definition criteria for neuroborreliosis. Both patients had positive serum and cerebrospinal fluid serology, a positive intrathecal anti-Borrelia antibody index, and a good outcome on ceftriaxone. Specific diagnosis of Lyme ON is important since improvement of visual acuity is possible with specific antibiotherapy, even after many months.