A reflex sight (10) comprises a housing (20) fitted with a proximal aperture (21) and a distal aperture (22) along an optics axis (A). It further includes a projection unit (40) reproducing the light generated by a light source (50) as a target mark (Z), and a feed optics (60) feeding the target mark (Z) reproduced by the projection unit (40) into the beam along the optic axis (A). To preclude the target mark (Z) from being visible to the sighted object, the invention provides that at least one implementing means (61, 62) of the invention be used whereby the target mark (Z) reproduced by the projection unit (40) substantially shall be visible only from the proximal aperture (21). The implementing means (61, 62) of the invention may be a polarizing beam splitting layer (61) designed as an interface layer (65) between two prisms (63, 64). Alternatively a band blocking filter (62) may be used which is configured between the feed optics (60) and the distal aperture (22) and which precludes light reflected by the feed optics (60) from passing through the distal aperture (22) by blocking/filtering such light. To attain economic and simple manufacture of the sight (10), the components (40, 50, 60, 70, 80, 90, 100) of the sight (10) are prefabricated sub-assemblies that can be installed rapidly and accurately in the housing (20).