The Fars news agency reported that Abdollah Bagheri Niakari was killed while fighting alongside Syrian government forces against "terrorists" in the northern city of Aleppo.
Earlier this month, two senior commanders in Iran's Revolutionary Guard, Gen Farshad Hasoonizadeh and Gen. Hossein Hamedani, were killed near Aleppo.
Iran is a longtime ally of Syrian President Bashar Assad and has provided crucial economic and military backing throughout the uprising and subsequent civil war.
Iran says it has sent military advisers to Syria but no combat troops.