PURPOSE Mild slipped capital femoral epiphyses (SCFE) nevertheless show significant femoral head-neck deformities which may put cartilage and acetabular labrum at risk. Whether this deformity can be restored to normal has not yet been described in the literature. METHODS In a prospective follow-up study, 14 patients with mild SCFE underwent in situ fixation with a single 6.5-mm cancellous, partially threaded screw. In 14 patients arthroscopic osteochondroplasty was performed, and in 13 patients pre- and postoperative measurements of the α-angle were made using antero-superior radial magnetic resonance imaging. RESULTS After arthroscopic osteochondroplasty, the mean α-angle decreased from 57° (range 50°-74°) to 37° (range 32°-47°; p < 0.001). Six patients showed beginning degenerative intra-articular changes (four antero-superior cartilage and three antero-superior labrum lesions) at the time of hip arthroscopy. No intra-operative complications occurred. In one patient, arthroscopic debridement was necessary due to arthrofibrosis and persistent pain. CONCLUSION Arthroscopic osteochondroplasty can successfully correct the antero-superior α-angle in patients with mild SCFE to normal values. Clinical randomized controlled studies with long-term follow-up are required to find evidence of improved functional and radiographic mid- and long-term outcome compared to in situ fixation alone.