An engine lubrication system having a lubricating oil pump that is rotationally driven by a crankshaft to send under pressure a lubricating oil to a part needing to be lubricated. The lubricating oil pump is connected to an end of a crankshaft such that a pump shaft aligns with the crankshaft substantially coaxially. An in-pump oil supply passageway is formed in the lubricating oil pump to pass therethrough from a side opposite the crankshaft to a side of the crankshaft. The in-pump oil supply passageway communicates at one end with an in-crankshaft oil supply passageway formed in the crankshaft for supplying a lubricating oil to a part of the crankshaft and at the other end with a discharge port of the lubricating oil pump via a lubricating oil passageway.