Patients undergoing thyroidectomy with neck fully extended usually experience occipital headache and posterior neck pain. We have attempted to evaluate the effect of preoperative greater occipital nerve (GON) block on occipital headache and posterior neck pain after thyroidectomy. Eighty-two patients undergoing elective total thyroidectomy were randomly allocated to two groups. In block group, bilateral GON blocks with 0.25% bupivacaine were performed. The control group did not have any prior block. Occipital headache and posterior neck stiffness were assessed using the visual analogue scale (VAS) and verbal rating scale. VAS of occipital headache and posterior neck pain in block group was significantly lower compared to that in the control group at postoperative 12 and 24 hours (p < 0.05). In addition, the proportion of patients reporting moderate or severe occipital headache and posterior neck pain at postoperative 12 and 24 hours in block group was significantly lower than that in control group (p < 0.001). No side effects were observed during and after GON block. We conclude that preoperative GON block with 0.25% bupivacaine is an effective technique to reduce occipital headache and posterior neck pain after thyroid surgery.