A lubricating oil composition for an internal combustion engine, prepared by blending: 0.5 to 5% by mass, based on the total amount of the composition, of a perbasic calcium sulfonate and/or a perbasic calcium phenate having a total base number, as measured by a perchloric acid method, of 200 mgKOH/g or higher; a binuclear organic molybdenum compound represented by general formula below and/or a trinuclear organic molybdenum compound represented by general formula below; and 2 to 20% by mass, based on the total amount of the composition, of a polyalkyl (meth)acrylate having an SSI of 30 or lower, into a lubricating base oil composed of a mineral oil and/or a synthetic oil, wherein the lubricating base oil has a kinematic viscosity at 100°C in the range of 2.0 to 10 mm 2 /s measured using a glass capillary viscometer according to JIS K2283-1983, wherein the total content of molybdenum derived from the binuclear and trinuclear organic molybdenum compounds is 0.025% by mass or higher based on the total amount of the composition, and wherein the lubricating oil composition has a high-temperature high-shear viscosity at 100°C of 4.0 to 5.0 mPa·s, a high-temperature high-shear viscosity at 150°C of 2.5 mPa·s or lower and a NOACK value measured at 250°C for 1 hr of 15% by mass or less, measured according to the method specified in ASTM D5800, wherein R 1 to R 4 represent a C 4 to C 22 hydrocarbon group and may be identical to or different from each other, and X 1 to X 4 each represents a sulfur atom or oxygen atom Mo 3 S k L n Q z wherein L's each independently represents a ligand having an organic group containing a carbon atom and at least 21 carbon atoms are present in total in all the organic groups of the ligands; n is from 1 to 4; k is from 4 to 7; Q represents a neutral electron donating compound; and z is from 0 to 5 and includes non-stoichiometric values, wherein the high-temperature high-shear viscosity at 100° and 150°C is measured by the method of ASTM D4683 and ASTM D6616 using a tapered bearing simulator viscosmeter and adopting the following test conditions: shear rate: 10 6 sec -1 rotational speed (motor): 3000 rpm clearance (rotor/stator): 3 μm oil temperature: 100°C and 150°C. 0.5 to 5% by mass, based on the total amount of the composition, of a perbasic calcium sulfonate and/or a perbasic calcium phenate having a total base number, as measured by a perchloric acid method, of 200 mgKOH/g or higher; a binuclear organic molybdenum compound represented by general formula below and/or a trinuclear organic molybdenum compound represented by general formula below; and 2 to 20% by mass, based on the total amount of the composition, of a polyalkyl (meth)acrylate having an SSI of 30 or lower, into a lubricating base oil composed of a mineral oil and/or a synthetic oil, wherein the lubricating base oil has a kinematic viscosity at 100°C in the range of 2.0 to 10 mm 2 /s measured using a glass capillary viscometer according to JIS K2283-1983, wherein the total content of molybdenum derived from the binuclear and trinuclear organic molybdenum compounds is 0.025% by mass or higher based on the total amount of the composition, and wherein the lubricating oil composition has a high-temperature high-shear viscosity at 100°C of 4.0 to 5.0 mPa·s, a high-temperature high-shear viscosity at 150°C of 2.5 mPa·s or lower and a NOACK value measured at 250°C for 1 hr of 15% by mass or less, measured according to the method specified in ASTM D5800, wherein R 1 to R 4 represent a C 4 to C 22 hydrocarbon group and may be identical to or different from each other, and X 1 to X 4 each represents a sulfur atom or oxygen atom Mo 3 S k L n Q z wherein L's each independently represents a ligand having an organic group containing a carbon atom and at least 21 carbon atoms are present in total in all the organic groups of the ligands; n is from 1 to 4; k is from 4 to 7; Q represents a neutral electron donating compound; and z is from 0 to 5 and includes non-stoichiometric values, wherein the high-temperature high-shear viscosity at 100° and 150°C is measured by the method of ASTM D4683 and ASTM D6616 using a tapered bearing simulator viscosmeter and adopting the following test conditions: shear rate: 10 6 sec -1 rotational speed (motor): 3000 rpm clearance (rotor/stator): 3 μm oil temperature: 100°C and 150°C. wherein R 1 to R 4 represent a C 4 to C 22 hydrocarbon group and may be identical to or different from each other, and X 1 to X 4 each represents a sulfur atom or oxygen atom Mo 3 S k L n Q z wherein L's each independently represents a ligand having an organic group containing a carbon atom and at least 21 carbon atoms are present in total in all the organic groups of the ligands; n is from 1 to 4; k is from 4 to 7; Q represents a neutral electron donating compound; and z is from 0 to 5 and includes non-stoichiometric values, wherein the high-temperature high-shear viscosity at 100° and 150°C is measured by the method of ASTM D4683 and ASTM D6616 using a tapered bearing simulator viscosmeter and adopting the following test conditions: shear rate: 10 6 sec -1 rotational speed (motor): 3000 rpm clearance (rotor/stator): 3 μm oil temperature: 100°C and 150°C. shear rate: 10 6 sec -1 rotational speed (motor): 3000 rpm clearance (rotor/stator): 3 μm oil temperature: 100°C and 150°C.