The sciatic nerve can be injured through various mechanisms, including direct compression and ischemia related to traumatic events. Reports of iatrogenic sciatic nerve injury caused by misplaced intramuscular injections are rare. We present a case involving a 5-year-old patient who developed motor weakness and hypesthesia in the left lower extremity following an intramuscular injection of diclofenac into the left buttock. An electrodiagnostic study diagnosed the patient with an injury to the left sciatic nerve, primarily affecting its peroneal division. This diagnosis was later confirmed by radiologic evaluation. Following several weeks of rehabilitation, which included gait pattern correction, verbal cueing, and electrical stimulation therapy, the patient showed improvement in sensory deficits and motor impairment. The peroneal portion of the sciatic nerve is more susceptible to injury than the tibial portion due to its structural characteristics. Additionally, the sciatic nerve follows various paths as it passes the piriformis muscle. Certain drugs, such as diclofenac, exhibit greater neurotoxicity than others. When neurologic deficits are observed, an electrodiagnostic study is recommended. This helps not only in identifying the etiology and precise location of the neural insult but also in predicting the prognosis and formulating a comprehensive treatment plan.