[Problem] To provide a lubricating oil composition for internal combustion engines, which has excellent fluidity in a low temperature environment, while maintaining high shear stability, and which has low agitation resistance with respect to an engine, while exhibiting excellent stability of thermal oxidation resistance. [Solution] A lubricating oil composition for internal combustion engines, which contains a lubricant base oil and a liquid random copolymer of ethylene and an α-olefin, said random copolymer being produced using a specific catalyst, and which is configured such that: the kinematic viscosity at 100°C is 12.5 mm²/s or more but less than 26.1 mm²/s; and the lubricant base oil is composed of a mineral oil that has a kinematic viscosity at 100°C of 2-10 mm²/s, a viscosity index of 95 or more and a pour point of -10°C or less and/or a synthetic oil that has a kinematic viscosity at 100°C of 1-10 mm²/s, a viscosity index of 120 or more and a pour point of -30°C or less.