Mitochondrial disease, which was previously considered as a rare clinical entity, is presently identified as a significant cause of a broad range of muscle, cardiac, neurologic, as well as endocrine disorders. One of the rare mitochondrial diseases is Kearns–Sayre syndrome (KSS). Here, we present a case of a 22-year old male with progressive bilateral blepharoptosis of 5‑year duration, which was painless and not associated with diplopia or vision loss. There were no similar abnormalities in his family. On neurologic examination, prominent bilateral blepharoptosis was evident with restriction of ocular movements. There was a salt‑and‑pepper pigmentary retinopathy with normal optic disks and vessels. Cerebrospinal fluid protein concentrations were increased, and a diagnosis of KSS was made.