We report a case of unilateral transient mydriasis and ptosis after botulinum toxin injection applied by a medical doctor for a cosmetic procedure. A 36-year-old nurse was referred to our eye clinic with unilateral mydriasis and ptosis in the right eye 3 days after botulinum toxin injection for a cosmetic procedure. Botulinum toxin was applied to her eye by a doctor at her hospital who was not an ophthalmologist. She was treated with topical apraclonidine 0.5% ophthalmic solution. Her ptosis decreased to 2 mm with apraclonidine and her visual axis improved. Mydriasis was present for 3 weeks and then disappeared. Mild ptosis continued for 3 months, then resolved completely. Patients seeking treatment with botulinum toxin A for cosmetic purposes should be warned about the possibility of ptosis and mydriasis after injection. If these side effects are seen, the patient must be referred to an ophthalmologist for appropriate management.