Acupuncture is one of the most popular complimentary therapies these days not only in Asia, but also in USA and Europe. Acupuncture is generally regarded as a safe procedure in the general public. However, acupuncture is not free of risk; complications of acupuncture have been repeatedly reported in the medical literatures. The authors report a rare case of hemorrhage in the cisterna magna after acupuncture. Acute frontal headache, dizziness, neck pain, neck stiffness, and paresthesia or tingling discomfort at arms and legs developed immediately after an acupuncture treatment that had been performed to treat her chronic posterior neck pain. Computerized tomography scans and magnetic resonance images(MRI) showed a 1.2x0.8cm-sized high density and high signal mass within the cisterna magna. It is probable that the acupuncture needle had been inserted deep enough to enter the cisterna magna and provoked a small hemorrhage in the cistern. She gradually recovered from the symptoms. Physicians and acupuncture therapists should be aware of the adverse events associated with acupuncture.