An objective lens system for endoscope comprising at least a first negative lens element, a second positive lens element, an aperture stop, and a cemented lens component consisting of a third negative lens element and a fourth positive lens element, and being configured so as to satisfy the conditions (2), (5) and (4) or the conditions (2), (3) and (4) which are mentioned below, whereby the lens system corrects lateral chromatic aberration and longitudinal chromatic aberration with a good balance, favorably corrects aberrations such as chromatic aberration and has a compact composition or a short total length. D2/f