Abstract: An improved through-door viewing device comprising a generally rectangular telescope, a lens mounted in one end of said telescope, an eyepiece mounted in the opposite end of said telescope, a window formed in one side of said telescope adjacent said one end, an escutcheon mounting said telescope in a door for sliding and rotating motion within said escutcheon, a mirror mounted within said telescope and pivotable between a first retracted position lying substantially parallel to the wall of said telescope out of the line of vision through said telescope and a second extended position lying across said line of vision in position to direct vision from said eyepiece through said window of said telescope, flange means responsive to inward sliding of said telescope to move said mirror to said retracted position, and spring means responsive to sliding of said telescope outwardly to urge said mirror to said extended position.