The effects of sodium hydroxide and urea on the gelatinization of corn starch suspensions, a main component of corrugating starch adhesives, were studied using differential scanning calorimetry (DSC). Sodium hydroxide and urea decreased the gelatinization starting temperature ( T _s1), peak temperature, conclusion temperature, enthalpy of gelatinization (DSC ΔH ), apparent activation energy (Ap E a), and van’t Hoff enthalpy change ( ΔH _vHº). DSC analysis showed the gelatinization endotherm, the melting endotherm of starch−lipid complexes, and an exotherm attributable to the alkali-decomposition of starch. This exotherm was only observed in the first scan for sodium hydroxide additions of more than 3.8 mol%. The existence of the starch−lipid complexes was also suggested by the reappearance of the corresponding endotherm in the second DSC scan. The increases in the gelatinization rate constants caused by the two additives were deduced from the Arrhenius equation using Ap E a. The relationship between the temperature corresponding to the half gelatinization transition ( T _m) and DSC ΔH , and that between T _m and Ap E a quantitatively agreed for the two additives, suggesting that gelatinization might be stimulated by a similar mechanism involving breaking intermolecular hydrogen bonds in starch. Only sodium hydroxide caused a significant decrease of T _s1 and broadening of the gelatinization peak. Therefore, ΔH _vHº and the size of the gelatinizing cooperative unit estimated from the ΔH _vHº/DSC ΔH ratio were decreased more by sodium hydroxide than by urea, indicating that sodium hydroxide facilitated the mobility of starch molecules more effectively during gelatinization.