The purpose of this report was to describe the surgical technique for and outcomes after a modified physeal-sparing posterolateral corner reconstruction in a 12-year-old skeletally immature male with a mid-substance fibular collateral ligament tear, a proximal posterior tibiofibular ligament tear, and an anterior cruciate ligament avulsion fracture of the medial tibial eminence. A modified physeal-sparing posterolateral corner reconstruction was used to provide a near-anatomic reconstruction of the fibular collateral ligament and proximal posterior tibiofibular ligament. An anterior cruciate ligament repair was also performed. Varus stress radiographs obtained at 6 months post-operatively demonstrated resolution of lateral knee stability. Physical examination results demonstrated stability to anterior tibial translation and a stable proximal tibiofibular joint. Computed tomography showed that the surgical technique successfully avoided breeching the patient’s physes.