Monocular elevation deficiency is the inability to elevate the eye in abduction and adduction. Myasthenia gravis could mimic any pattern of ophthalmoplegia. However, myasthenia gravis mimicking monocular elevation deficiency appears to be very rare. A 12-month-old girl presented with the inability to elevate the left eye and blepharoptosis from 3 months of age. A neostigmine test showed a weakly positive response. Repetitive stimulation of the left orbicularis oculi produced no decremental response. Three assays for acetylcholine receptor antibodies were negative. Placing ice over the lids definitely improved left blepharoptosis. In conclusion, myasthenia gravis could mimic elevation deficiency. An ice test could be very helpful in making the diagnosis. Myasthenia gravis should be included in the differential diagnosis of monocular elevation deficiency even at a young age.