Abstract: In an ignition control system, a primary current control unit performs discharge generation control one or more times during a single combustion cycle. The discharge generation control allows a spark plug to generate a discharge spark. A parameter calculating unit successively calculates a parameter correlated with energy of a discharge spark. An energy density calculating unit successively calculates energy density that is energy per unit length of the discharge spark. When the energy density is greater than a predetermined value during a predetermined period after a primary current is interrupted during a single combustion cycle, an integrated value calculating unit calculates an integrated value by integrating the parameter during the predetermined period. The primary current control unit performs the discharge generation control again when the integrated value calculated by the integrated value calculating unit is less than a predetermined determination threshold.