Rhabdomyosarcoma is exceptionally rare in the adult population, comprising less than 0.03% of all adult malignancies. We describe the diagnosis and management of a 43-year-old patient who developed a primary rhabdomyosarcoma arising in the tibialis anterior muscle (TA) adjacent to a left latissimus dorsi (LD) free muscle transfer to his right leg following reconstruction for an open tibia and fibula fracture in 2009. In 2024, the patient presents to a specialist tertiary sarcoma service with a 6-month history of painless lump to his shin. Clinically, it was difficult to distinguish if the lump originated from the LD flap or a heavily traumatised TA muscle following the previous open fracture. Rhabdomyosarcoma was diagnosed on an incisional biopsy. An MRI demonstrated that the sarcoma was likely arising from the TA. The patient subsequently underwent limb-salvaging resection of the anterior compartment of his right leg followed by reconstruction with a pedicled gastrocnemius flap. This is the first known case report described in Australia.