The effects of TiO2 addition on the reaction behavior, product, and mechanism in the Ti–B4C system were investigated in this study. The reaction could be self-sustaining for the TiO2 addition no more than ∼33% of the total weight of the reactants. With an increase in the TiO2 addition, the combustion temperature and wave velocity decrease progressively, the ignition delay time first decreases and then increases, while the constituents of the reaction products do not vary significantly unless the relative addition content of TiO2 exceeds ∼22 wt%. Therefore, TiO2 could be used as a favorable reaction regulator for the Ti–B4C system. The reaction mechanism, as determined by differential thermal analysis and combustion front quenching experiment in combination with subsequent x-ray diffraction examination, is changed more or less by the addition of TiO2 with the extent depending on the addition amount.