Abstract: The invention relates to a multi-piston hydraulic pump for a free-piston engine, comprising two engine pistons (2) mounted on a common piston rod (1) which is also fitted with pin-shaped pistons (5a, 5b) of the hydraulic pump at a radial distance from the piston rod (1). Mounting blocks (6a,6b) for the hydralic punp pistos (5a, 5b) extend from the engine piston rod (1) crosswise relative to each other at an axial distance from each other. The hydraulic pistons (5a and 5b) fastened to different mounting blocks (6 and 6b and 6b) are located for the most part side by side over the same section of the axial length of the engine piston rod and the free ends thereof point in opposite directions.