Introduction: Malignant diseases with infiltration of bony structures in the area of the phalanges or metacarpals require either amputation or complex reconstruction. The decision for reconstruction means to restore length, mobility, sensibility, stability as well as aesthetics. Methods: We present a case of complex first ray reconstruction of the left hand using a free osteocutaneous lateral arm flap from the ipsilateral side. The reconstruction was performed after radical resection of an exulcerated squamous cell carcinoma, including the first metacarpal bone, trapezium, partial trapezoid and distal scaphoid as well as partial resection of the extensor pollicis longus, extensor pollicis brevis, abductor pollicis longus and flexor carpi radialis tendons. The osteosynthetic restoration was achieved distally by a double wire cerclage and a proximally by temporary K-wire suspension. Moreover, to reconstruct the extensor pollicis longus tendon the ipsilateral palmaris longus tendon was harvested and used. Postoperatively, a secondary humerus fracture occurred, which was initially attended by plate osteosynthesis. The fracture showed delayed healing, which was treated by re-plating and autologous cancellous bone. Results: 12 months postoperatively, the patient showed an excellent outcome with length preservation and good range of motion, sensibility, stability and aesthetic of the thumb. Furthermore, the quarterly tumor aftercare showed no evidence of recurrence. Conclusion: This case report showed that the free osteocutaneous lateral arm flap is a reliable solution for the reconstruction of the first ray with a great functional and aesthetic outcome. To prevent a secondary humerus fracture, a preventive plate osteosynthesis simultaneous with the osteocutaneous flap elevation should be considered.