We describe a 42-year-old patient who incurred long thoracic nerve palsy after using one axillary crutch. The patient sustained fractures to his left tibia and fibula. The fractures required internal fixation with a locked intramedullary nail and postoperative restricted weightbearing using axillary crutches. When weightbearing was progressed, the patient began using one axillary crutch on the right side. The resulting asymmetric gait pattern forced the crutch onto his chest wall, which led to right-sided long thoracic nerve palsy. The patient had not recovered 6 months after the injury. When providing axillary crutches, clinicians must consider potential compromise of the long thoracic nerve and the brachial plexus if the crutch is used inappropriately.