The invention relates to an internal combustion engine (1) having a cylinder head (2) and a cylinder block (3), wherein a crankcase (10) is fastened to the cylinder block (3), wherein at least one mass balancing shaft (20) is mounted in the crankcase (10). In order to reduce the production effort, according to the invention, a first pin (26) designed as a dowel pin is positioned in the region of the end face (5) of the crankcase (10) disposed in a hole (6) on a straight connecting line (27) between the axis (20a) of the mass balancing shaft (20) and the axis (19a) of the crankshaft (19) as seen in the direction of the axis (19a) of the crankshaft (19), wherein the first pin (26) is preferably disposed in the crankcase (10) and the hole (6) is preferably disposed in the flange bushing (24).