Flexion contracture of the elbow is a common deformity associated with brachial plexus birth palsy and is often managed with preventive night orthoses. For severe cases, however, surgical interventions may become necessary. This study evaluated the effectiveness of surgically releasing elbow flexion contractures exceeding 30° through partial tenotomy of the brachialis and biceps brachii muscles, along with a division of the lacertus fibrosus. We performed 36 anterior elbow releases on patients with injury to the upper trunk (C5-C6) of the brachial plexus and elbow flexion contractures between 30° and 80°. All releases involved lacertus fibrosus section and partial lengthening of the distal portion of the brachialis tendon. In severe cases, biceps brachii tenotomy was also performed. All participants had a minimum follow-up of 12 months and preoperative elbow flexion strength of at least grade 4 on the British Medical Research Council scale, with no deformities in the shape of the ulnohumeral joint or radial head subluxation. Following a mean follow-up of 41 months, the average extension gain was 31° (range, 10°-50°). All patients maintained their flexion strength. Except for two participants with weaker triceps, the mean elbow extension gain was sustained throughout the follow-up period. There were no major or minor complications or reinterventions in the study. Partial tenotomy of the brachialis and biceps brachii muscles, coupled with lacertus fibrosus section, is an effective treatment for elbow contractures exceeding 30° flexion. This method is successful in individuals with a functioning triceps brachii and elbow extension strength of at least grade 3 on the British Medical Research Council scale. Therapeutic IV.