INTRODUCTION: The primary goals of mandibular reconstruction are to restore form, function, and aesthetics while providing a platform suitable for implant placement and oral rehabilitation. We used a novel custom endoprosthesis with complementary cutting guides and predrilled holes to mirror the angle and slope of the native mandible; the upper portion conforms to the bone graft and a medial titanium ledge supports the bone in a cephalad position to optimize distance from the occlusal plane. METHODS: This is an IRB-approved, retrospective chart review at high-volume plastic and maxillofacial surgery departments at pediatric tertiary-care referral centers between January 2018 and June 2021. Patient demographics, comorbidities, mandibular pathology, lesion size, endoprosthesis specifications, postoperative complications, and follow-up time were collected. RESULTS: Eleven patients underwent mandibular resection and custom endoprosthesis reconstruction with free fibula bone osteocutaneous flaps (n = 9), rib graft (n = 1), and iliac crest bone graft (n = 1). Immediate postoperative CT scans confirmed endoprosthesis placement. Five patients (45%) required revisional surgery for distal flap necrosis (n = 1), a small intraoral granuloma (n = 1), and orocutaneous fistulas (n = 3), of which one resulted in endoprosthesis removal. One patient experienced transient foot drop. Excellent cosmetic outcomes were achieved in all patients. Thus far, two patients (18%) have completed dental restoration. CONCLUSION: This custom endoprosthesis represents an untapped avenue toward more comprehensive mandibular reconstruction. It shows compatibility with microvascular flaps as well as skeletally immature and mature patients alike. By optimizing facial contour and bone height, this novel endoprosthesis is an attractive option for patients whose ultimate goal is dental restoration.