Myofascial pain affects about 10% of the United States population, often involves the trapezius muscle, and can be difficult to manage using conventional analgesic medications in the Emergency Department (ED). The use of ultrasound-guided nerve blocks performed by emergency physicians is well-documented, but this is the first report describing the technique and effectiveness of an ultrasound-guided spinal accessory nerve block for acutely treating trapezius myofascial pain in the ED setting. In this case series of three patients with intractable trapezius pain, the ultrasound-guided spinal accessory nerve block proved feasible and offered substantial therapeutic benefit.