We describe a 44-year-old female with triple-negative breast cancer who developed skin erythaema, sclerosis and contracture of her entire right breast 15 months after completion of post-lumpectomy chemotherapy and radiotherapy, consistent with post-irradiation morphoea (PIM). PIM is a rare complication of breast irradiation that impairs a patient's quality of life. PIM is located usually at the radiation port or in the surrounding tissue. Clinically, PIM is misdiagnosed commonly as lymphoedema and cellulitis in the early inflammatory phase, and recurrent breast cancer, chronic radiodermatitis (CRD), radiation-induced fibrosis (RIF), post-irradiation pseudosclerodermatous panniculitis (PIPP), atypical vascular lesions (AVL) or angiosarcoma (AS) in the late burnout phase. Arriving at the correct diagnosis typically requires a multidisciplinary approach, including a skin biopsy for confirmation. To date, satisfactory treatment of this condition has been challenging. and the clinical outcome after therapy is often unsatisfactory.