The purpose of this study was to report on 12 patients with acquired strabismus following cosmetic blepharoplasty and to identify patterns of strabismus related to the surgical procedure. Clinical ophthalmologic examinations were performed to specifically clarify the type of strabismus. Operative reports of the blepharoplasty procedures were reviewed. Patients were followed for a minimum of 3 months after the blepharoplasty procedure before surgical intervention was considered. Operative findings at corrective strabismus surgery were noted and an attempt was made to correlate these findings with the clinical ophthalmologic examination and the blepharoplasty surgical procedure. Twelve cases of persistent vertical strabismus occurred following blepharoplasty procedures. Five patients had clinical findings consistent with the diagnosis of acquired superior oblique palsy; one of these five patients also showed signs of an acquired Brown syndrome. Seven patients developed an incomitant vertical deviation consistent with an inferior rectus paresis. Strabismus occurred after conventional lower lid, upper lid, and four-lid blepharoplasty with or without laser blepharoplasty. Acquired strabismus accompanied by persistent diplopia may occur as a complication of cosmetic blepharoplasty. Extraocular muscle damage resulting in either superior oblique muscle palsy or inferior rectus paresis was noted in these patients. In some cases, patients with inferior rectus paresis also showed mechanical restriction to upward rotation of the globe.