An ignition coil for an internal combustion engine includes: an iron core; a primary coil wound around the iron core via a primary bobbin; a secondary coil provided to externally surround the primary coil; a ground terminal fitting placed with a part thereof being held between the primary bobbin and the iron core; and a resin-molded portion provided to cover the primary coil and the secondary coil, a ground side terminal portion of the primary coil being connected to the ground terminal fitting, wherein at least one protrusion is formed in the part of the ground terminal fitting held between the primary bobbin and the iron core, and the protrusion has a pointed tip that is brought into contact with the iron core.