Pathological fractures associate a complex tumoral microenvironment that can culminate in a complex bone nonunion. Surgical treatment with vascularized periosteal flaps has resulted into an excellent option in children because of their angiogenic and osteogenic properties; nonetheless, it has been scarcely reported in the adult. We present a case report that challenges the classical concept of not using pure periosteal flaps in the adult, widening surgical options for nonunion. A 67-year-old male patient diagnosed with multiple myeloma presented nonunion after pathological fracture in the left humerus. He was treated with a pedicled lateral humeral pure periosteal flap based in the posterior collateral radial vessels. It measured a 6 cm × 4 cm and was pedicled proximally, wrapping it around the nonunion site after compression plate osteosynthesis. Post operatory was uneventful and the patient was followed 9 months after surgery. Periosteal callus and bony bridges were formed 4 months after surgery. This case avoids the need of a free flap such as the Sakai, with conservation of the advantages of the cambium layer such as demonstrated in children.