© 2017 Wiley Periodicals, Inc. Purpose: Nonunion is a common complication of lateral condyle humeral (LCH) fractures in children. In situ fixation with a screw and bone grafting is the classically-recommended method of treatment. The purpose of this study is to analyze the feasibility of obtaining a vascularized periosteal flap obtained from the lateral humerus and based on the posterior collateral radial vessels (PCRV). Second, to report the results after the application in two pediatric cases. Methods: Periosteal branches of PCRV were studied in ten upper limbs from fresh human cadavers. Then, two children with LCH nonunion were treated with this flap. Results: The PCRV provided mean of 5.3 anterior periosteal branches (range 4–7) with a mean distance between them of 19.1 mm (range 5–29 mm) and 5.7 posterior periosteal branches (range 3–7) with a mean distance between them of 15.9 mm (range 6–33 mm. PCRV distally anastomosed to the interosseous recurrent artery and the radial recurrent artery, creating a vascular net over the lateral condyle and allowing for the design of a reverse vascularized humeral periosteal flap (VHPF). Abundant periosteal callus and rapid consolidation were achieved in both children. No bone fixation or grafting was necessary. Conclusions: VHPF might be considered a viable biological surgical option to promote bone healing in LCH nonunions in children, while avoiding the need for bone fixation and the donor morbidity associated with bone grafting.