Malformation and hypoplasia of the clavicle can result in pain, impaired function, restricted shoulder movement, subjective feeling of instability and cosmetic deformity. There are no reports of clavicle lengthening by osteotomy and distraction osteogenesis (DO). This is a retrospective review of 5 patients (7 clavicles) who underwent clavicle lengthening by DO using a monolateral external fixator for clavicular hypoplasia. There were 3 males and 2 females with mean age 15 years (9 to 23) and mean follow-up 21 months (8 to 51). Preoperative diagnoses included Klippel-Feil syndrome, cleidocranial dysplasia with torticollis, congenital myopathy and Noonans syndrome and obstetric brachial plexus injury. Mean length gained was 31 mm (15 to 41) which represens an average of 24.7% of overall bone length. Mean time in fixator was 174 days (161 to 263) and mean external fixation index was 56 days/cm. Two patients required internal fixation following fixator removal to consolidate union and one required additional internal fixation for atrophic regenerate. Mean preoperative oxford shoulder score improved from 28.5 to 41 and all patients were extremely satisfied with their result. Two patients developed pin site infections. Clavicular lengthening by distraction osteogenesis for congenital clavicular hypoplasia is a previously unreported technique that enables gradual correction of deformity without risking brachial plexus traction injury following acute correction. It has the potential to improve shoulder pain, function, range of movement and cosmesis. Distraction ≥25% of overall bone length may require additional plate fixation to consolidate union