Myasthenia gravis (MG) is the most common disease of the neuromuscular junction disorders with bimodal distribution of age, which is often under-estimated in the elderly. Some clinical cases show an association between MG and COVID-19, since molecular mimicry between SARS-CoV-2 and AChR proteins could be responsible for the onset of the disease. We report a 77-year-old woman who developed right eyelid ptosis five days after COVID-19 infection. Positive serum anti-acetylcholine receptor antibodies allowed the diagnosis of myasthenia gravis. It should be noted that there were no significant decremental changes on 3 Hz repetitive motor nerve stimulation study, even for the affected orbicularis oculi muscle. Clinical and pathophysiological data suggest that inflammation during COVID-19 could trigger an overproduction of autoantibodies previously present in the body at a subclinical level. This is the first case of COVID-19 infection complicated by myasthenia gravis, to the best of our knowledge, that resolves spontaneously.