Compartment syndrome of the arm is a rare event that can be subsequent to trauma or other pathological and physical conditions. At the arm the thin and elastic fascia may allow accumulation of blood more than in other districts, especially in patients undergoing anticoagulant therapy. We describe a rare case of an acute compartment syndrome of the arm after minor trauma with partial biceps brachii rupture in a patient with warfarin therapy and optimal value of INR. Prompt diagnosis and surgical decompression helped to avoid the occurrence of complications with a satisfying recovery of arm function.