The invention provides a highly compact hydraulic tappet for an internal combustion engine. The highly compact hydraulic tappet for the internal combustion engine comprises a tappet body, a plunger sleeve and a plunger. The tappet body, the plunger sleeve and the plunger are coaxially arranged. The upper end of the tappet body is open, and the plunge sleeve can be in clearance sliding fit with theinner side wall of the tappet body in the axial direction. The plunger sleeve is of an H-shaped structure, the plunger is of a T-shaped structure, and the plunger can be in clearance sliding fit withthe inner wall of the upper portion of the plunger sleeve in the axial direction. According to the highly compact hydraulic tappet for the internal combustion engine, through the combined applicationof the tappet body, the plunger sleeve and the plunger, the valve clearance of the engine can be effectively eliminated, the structure is simple, the number of parts of traditional hydraulic tappetscan be greatly reduced, and the high compactness can be realized.