An objective lens system for endoscopes comprising, in order from the object side, a first lens unit having negative refractive power, a second lens unit having positive refractive power and a third lens unit having positive refractive power; wherein astigmatism is corrected favorably by using an aspherical surface in the third lens unit or an aperture stop is arranged between the second lens unit and an image surface of the objective lens system, and aberrations including chromatic aberration are corrected favorably.