A sealing system for oscillating-piston engines that include two oscillating pistons that revolve together in a spherical housing. The pistons perform reciprocating oscillating movements in opposite directions about an oscillation axis perpendicular to the axis of revolution for the pistons. Guide members are provided on the pistons and engage at least one guide groove formed in the housing. Sealing elements are disposed on or in the vicinity of all moving edges surrounding working chambers and prechambers for the engine. The sealing elements seal all the gap regions present between machine parts displaced relative to one another by revolving and/or oscillating movements and not in direct contact. Sealing elements prevent excessive penetration of lubricating fluid into inlet and outlet openings in the housing.