BACKGROUND: Desmoid fibromatosis is a rare, sarcoma-like neoplasm that aggressively invades surrounding soft tissue and is often quite painful. Surgery has historically been the mainstay of treatment. Given the high rates of recurrence and unpredictable nature of the lesions, multidisciplinary therapy may be needed to provide adequate analgesia. CASE REPORT: A 35-year-old woman with a history of inoperable desmoid fibromatosis was evaluated in our chronic pain clinic for chest wall and axillary pain due to tumor recurrence. An erector spinae plane block markedly improved her level of pain and functional status. CONCLUSION: This case report highlights the use of a thoracic erector spinae plane block (ESPB) for an inoperable desmoid tumor of the chest wall. Thoracic ESPB is growing in popularity in the field of interventional pain management, but has few definitive indications due to its relative newness. This case report demonstrates that a thoracic ESPB can be a viable, multiregional pain relief strategy for chest wall tumors since our patient reported enduring pain relief, an improved quality of life, and decreased opioid use as a result of the procedure. KEY WORDS: Erector spinae plane block, desmoid fibromatosis, chronic pain, desmoid tumor, regional anesthesia, case report