Aim: This article aims to describe a novel surgical technique for medial malleolar reconstruction in a young child. Background: Severe open ankle injuries that result in bone and soft tissue loss carry a high risk for complications, especially in children who are still growing. These injuries can cause abnormal growth patterns, degenerative diseases, and recurrent instability. Cases of medial malleolar reconstruction have been previously described but none in a child this young. Case description: We present a case of an 13-year-old girl who suffered an open injury to the medial distal tibia with traumatic loss of the medial malleolus at the age of 2 and later suffered a Salter-Harris II fracture to the ipsilateral distal fibula. She presented with varus alignment, a leg length discrepancy, premature asymmetrical growth arrest, chronic non-union of the distal fibula physeal fracture, and severe attenuation of the deltoid ligament. Her secondary deformities were managed with distal fibula osteotomy and fixation, distal tibial hemi-plafond corrective osteotomy, and medial malleolus reconstruction with iliac crest autograft. Her leg length discrepancy was corrected by epiphysiodesis of the contralateral distal femur and proximal tibia. At the 2-year follow-up, the alignment was well maintained, the graft was healing well, and the patient reported no pain and being able to walk and play sports without a brace. Conclusion: Surgical reconstruction of the medial malleolus with correction for abnormal angulation and leg length discrepancies is critical to promoting healthy growth patterns and quality of life for paediatric patients. This severe open ankle injury can be successfully managed by distal fibula osteotomy and fixation, distal tibial intra-articular osteotomy, and medial malleolus reconstruction with iliac crest autograft. Clinical significance: This novel technique is an effective method for the surgical management of paediatric traumatic medial malleolar bone loss in children who are skeletally immature and are at risk of complications due to further growth.