Lacertus fibrosus entrapment of the median nerve at the elbow, or Lacertus syndrome, is a rare pathology, which is difficult to detect by instrumental examination methods. Literary sources provide no information on the syndrome prevalence, as well as on precise diagnosis and treatment algorithms, which makes it difficult to establish the diagnosis and appoint the effective treatment. Lacertus syndrome is characterized by positive scratch collapse test; differential diagnosis is required to distinguish it from carpal tunnel syndrome. Clinical case of bilateral lacertus fibrosus entrapment of the median nerve at the elbow is reported, Lacertus syndrome diagnosis criteria and surgical treatment method are set out. The results of the surgical tactics used are as follows: pain, paresthesia and numbness in the innervation field of the median nerve have vanished, the muscle strength has been restored to level М5 in accordance with MRC muscle strength scale. These results demonstrate high efficiency of the proposed lacertus syndrome surgical treatment.