The aim of this report is to investigate the possible causes of acute acquired onset of transient esotropia (AATE) in children and to help to differentiate ophthalmoplegic migraine (OM) from accommodative spasm (AS). A case of an 8-year-old Caucasian female affected by AATE and diplopia is described. The day before AATE onset, the patient complained of slight headache without nausea and vomiting, with spontaneous resolution. AATE diagnosis is challenging. The most likely ophthalmological causes of AATE are AS and OM. In these cases it is important to evaluate the presence of both a familial history of recurrent headaches and an AATE associated with migraine, ptosis, nausea, and vomiting. A full ophthalmological evaluation and a thorough refractive examination in cycloplegia are mandatory to exclude ophthalmological causes.