Supracondylar fractures of the humerus associated with ipsilateral forearm fractures are uncommon and treatment recommendations are controversial. The purpose of this study was to determine whether pin fixation of both fracture components, humerus and forearm, would improve the outcome. In a two-center trial, 884 children sustaining supracondylar fractures of the humerus were retrospectively reviewed, and 47 (5.3%) showed associated ipsilateral forearm fractures. Of those, 29 underwent Kirschner-wire fixation of the forearm fracture, and 18 of the forearm fractures were treated with casting alone. Three of the 18 forearm fractures with casting alone reangulated. There were no reangulations in the patients who had pin fixation of their fractures. There were no complications due to pin fixation in the humerus or the forearm. In unstable supracondylar humerus and forearm fractures, stabilization with pin fixation to prevent reangulation should be considered.