Transient anisocoria is rare during blowout fracture reconstruction. We report a case of transient anisocoria occurring during medial blowout fracture reconstruction and review the relevant literature. A 54-year-old woman was struck in the face and was admitted for a medial blowout fracture of the left eye. During the operation, persistent bleeding occurred. To control this bleeding, a 1% lidocaine solution with 1:200,000 epinephrine was applied to the orbital wall with cotton pledgets. In total, 40 mL of local anesthetic was used for the duration of the operation. After approximately three hours of the surgery, the ipsilateral pupil was observed to be dilated, with sluggish response to light. By 3 hours after the operation, the mydriasis had resolved with normal light reflex. In conclusion, neurological and ophthalmologic evaluation must be performed prior to blowout fracture surgery. Preoperative ophthalmic evaluation is simple and essential in ruling out any preexisting neurologic condition. Moreover, surgeons must be aware of the fact that excessive injection of lidocaine with epinephrine for hemostasis during orbital wall surgery can result in intraoperative anisocoria. Anisocoria-related situations must be addressed in a proficient manner through sufficient understanding of the mechanism controlling the pupillary response to various stimuli.