Purpose Morphea en coup de sabre, or French for “blow from a sword”, is a rare form of localised scleroderma characterised by progressive linear atrophy and frontocranial vertical depression, classically presenting in childhood. In this report, we present a rare case of adult-onset en coup de sabre successfully treated with single-stage autologous fat grafting. Methodology A 64-year-old man presented with a 7-year history of spontaneous right paramedian forehead linear depression, soft tissue atrophy, bony concavity, and alopecia. He was treated with single-stage autologous fat grafting using Coleman's technique, with retrograde injection of 20cc of fat and deliberate overcorrection to allow for fat resorption. Results At 6 weeks post-operatively, we achieved a satisfactory aesthetic outcome with the correction of contour deformity, volume stabilisation and minimal fat resorption. The patient reported high satisfaction with the aesthetic outcome and experienced no complications. Conclusion This case highlights that autologous fat grafting is a safe, effective and minimally invasive single-stage reconstructive treatment for stable craniofrontal linear scleroderma, including adult-onset presentations. Fat grafting provides both volumetric correction and potential regenerative benefits that address disease processes, making it a valuable option for residual deformity after disease quiescence.