An optical sight ensures a more accurate aim at feebly discernible targets in the twilight and in dull weather. The sight includes an objective, a reticule, an erecting system consisting of a first and a second positive component, each of which is cemented of two lenses, and an eyepiece. The sight also includes a beam-splitting cube, the beam-splitting face made as a diagonal face, three mirrors and a third positive component cemented of two lenses, a first plane mirror parallel to the beam-splitting face of the cube on the same axis with the third positive component, a second plane mirror perpendicular to the first mirror in front of a focal plane of the eyepiece, and a third mirror tilted to the optical axis and faced with its reflective surface toward the eyepiece arranged between the eyepiece focal plane and the second component of the erecting system.