Purpose: The purpose of the study was to answer the following questions. What was functional results of pediatric patients receiving a short stem allograft-prosthesis composite of the proximal femur? What was complication rate and revision-free implant survival? Was it possible to preserve the bone stock of the proximal femur in pediatric patients? Methods: We reviewed 10 pediatric patients treated with proximal femur resection for a primary bone tumor and reconstruction with short stem allograft-prosthesis composite, with at least 24 months follow-up. The median age was 9 years (4–13) at surgery. The mean resection length was 15 cm (6–29). In six cases, fixation was performed with a short plate positioned under the great trochanter while in four cases a long plate extended over the great trochanter was employed. Results: Nine complications that required surgical revision were assessed in six patients (one wound dehiscence, two nonunions, two fractures, one acetabular wear, three hypometria), while allograft-prosthesis composite removal was required in three patients. The revision-free survival was 57% (95% confidence interval 33%–100%) at 5 and 10 years. The graft removal-free survival was 75% (95% confidence interval 50%–100%) at 5 and 10 years. The mean Musculo-Skeletal Tumor Society Score was 28 (20–30). Conclusions: Allograft-prosthesis composites with short stem and compression plate represents an effective reconstructive option after proximal femur resection for primary bone tumors in growing patients, preserving bone stock. The use of a compression plate extended over the greater trochanter seemed to reduce failure rate.