Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder of the neuromuscular junction. LEMS can be associated with a variety of neoplasms. Patients present with proximal muscle weakness and fatigability, often combined with areflexia. Only 5% of reported cases are children. We report a case of 11-year old boy with non-neoplastic Lambert-Eaton myasthenic syndrome. Repetitive nerve stimulation test showed 83% increment after maximal voluntary contraction, presence of antibodies against voltage-gated calcium channels confirmed the diagnosis. The boy responded well to immunosuppressive treatment with prednisone and azathioprine and remains cancer-free for 4 years.