Patients with acquired adult-onset strabismus mainly present with binocular diplopia. Although cranial nerve palsies are reportedly the most common cause of binocular diplopia in adults, thyroid disease can also cause diplopia. In patients with thyroid-associated ophthalmopathy, upper lid retraction and proptosis are the most common initial findings, but diplopia could be the first manifestation. So far, there has been little information on the diagnostic value of thyroid autoantibodies in patients with strabismus. Therefore, we examined adults with acquired binocular diplopia from 2008 to 2016 and evaluated the presence of thyroid autoantibodies and the relationship between thyroid autoantibody status and clinical characteristics in adults with acquired binocular diplopia. Thyroid autoantibody tests were performed for all patients, unless other causes of diplopia were identified. Fifty one (39%) of 132 patients were positive for thyroid autoantibodies. In the thyroid autoantibody-positive (TAb+) group, microsomal autoantibodies, thyroid-stimulating hormone receptor antibodies, thyroglobulin antibodies, and thyroid-stimulating antibodies were observed in 30, 27, 12, and 7 patients, respectively. The vertical deviation and grade of duction limitation were greater in the TAb+ group. The presence of ocular torsion was 15.5% and 39.5% in the TAb- and TAb+ groups, respectively. Thyroid autoantibody evaluation may be helpful in adults with idiopathic acquired binocular diplopia.