Purpose: Surgery for thyroid gland requires skin incisions that can result in postsurgical neck scar. To overcome this, many surgeons performed a endoscopic thyroidectomy. But, this approach had a some problems. One of postoperative problems, iatrogenic cervical dystonia (CD) may occur. At common, CD is defined as a syndrome characterized by prolonged muscle contraction causing twisting, repetitive movements or abnormal posture. Botulinum toxin A (BTA, Botox$^{(R)}$, Allergan, Irvine, CA, USA) is well known treatment agent in the treatment of CD. So, the authors applied BTA injection in rare case with iatrogenic CD resulting in endoscopic thyroidectomy. Methods: A 43-year-old female had endoscopic subtotal thyroidectomy operation 3 years ago. She had symptoms such as progressive cervical pain, abnormal neck posture, depression, and sleep difficulty. About 1 year later, the patient who had previous myomectomy of the clavicular head of sternocleidomastoid muscle, however, symptoms were not improved. And then the patient received BTA therapy in our department. The 2 units per 0.1 mL solution was administered in a 1 mL tuberculin syringe. Results: The dose of BTA used in the patient was 36 units for vertical platysmal bands, superficially, and 10 units for ipsilateral sternocleidomastoid muscle, intramuscularly. After 2 weeks, additional the dose of BTA used in the patient was 5 points for remained scar bands, superficially. Complications related to injection such as significant swallowing difficulties, neck muscle weakness, or sensory change were not observed. In 9 months follow-up, the patient maintained a good result from the method of BTA injection alone. Conclusion: The basic concept is selective denervation for the hyperactive individual muscles and scar bands. We conclude that BTA is an effective and safe treatment for CD despite the iatrogenic and complex presentation of this complication.