Platelet-rich plasma (PRP) is an autologous concentrate enriched in growth factors. Its tissue-repairing effects have made PRP the focus of attention for use in tissue regeneration. PRP has been safely used in many fields, including orthopaedics and sports medicine. In the case examined here, a 67-year-old woman had left shoulder pain after a motor vehicle accident. She had long-standing post left lumpectomy upper-limb swelling due to breast cancer, which had been diagnosed well over a decade before. She developed stage 3 lymphoedema of the left arm and hand, which was refractory to comprehensive decongestive therapy and compression garment therapy. MRI of the left shoulder demonstrated a small partial-thickness tear of the rotator cuff. After failure of initial treatment with physical therapy and corticosteroid injection, she was referred for PRP treatment. Five days after the first PRP injection, the patient reported a complete resolution of lymphoedema in her left hand.