A cylinder lock monitor (16, 70) for monitoring a position of a cylinder lock including a rotating cam, the cylinder lock monitor (16, 70) comprising: a cylinder lock monitor housing (34, 72) adapted to be positioned proximate to the rotating cam of the cylinder lock, the cylinder lock monitor housing (34, 72) having an inner portion (40, 78) and defining a pass through opening (56, 86) through the inner portion (40, 78) of the cylinder lock monitor housing (34, 72) and an exterior diameter, the exterior diameter of the cylinder lock monitor housing (34, 72) being no greater than the corresponding cylinder lock diameter; a plunger (36, 74) having an inner portion, the plunger (36, 74) movably disposed in the pass through opening (56, 86) of the cylinder lock monitor housing (34, 72) for movement between a first position where the inner portion of the plunger (36, 74) extends from the pass through opening (56, 86) in the inner portion (40, 78) of the cylinder lock monitor housing (34, 72) and a second position where the inner portion of the plunger (36, 74) is pushed into the pass through opening (56, 86) in the inner portion (40, 78) of the cylinder lock monitor housing (34, 72); a spring (38, 76) disposed in the pass through opening (56, 86) of the cylinder lock monitor housing (34, 72) for biasing the plunger (36, 74) toward the first position; and a switch housed with the pass through opening (56, 86) of the cylinder lock monitor housing (34, 72), fixed or integral with the plunger (36, 74), the switch being in electrical communication with an indicator and adapted to be reactive to any change in position of rotating cam of the cylinder lock wherein the inner portion of the plunger (36, 74) is adapted to contact the rotating cam between and including the first and second positions of the plunger (36,74). a cylinder lock monitor housing (34, 72) adapted to be positioned proximate to the rotating cam of the cylinder lock, the cylinder lock monitor housing (34, 72) having an inner portion (40, 78) and defining a pass through opening (56, 86) through the inner portion (40, 78) of the cylinder lock monitor housing (34, 72) and an exterior diameter, the exterior diameter of the cylinder lock monitor housing (34, 72) being no greater than the corresponding cylinder lock diameter; a plunger (36, 74) having an inner portion, the plunger (36, 74) movably disposed in the pass through opening (56, 86) of the cylinder lock monitor housing (34, 72) for movement between a first position where the inner portion of the plunger (36, 74) extends from the pass through opening (56, 86) in the inner portion (40, 78) of the cylinder lock monitor housing (34, 72) and a second position where the inner portion of the plunger (36, 74) is pushed into the pass through opening (56, 86) in the inner portion (40, 78) of the cylinder lock monitor housing (34, 72); a spring (38, 76) disposed in the pass through opening (56, 86) of the cylinder lock monitor housing (34, 72) for biasing the plunger (36, 74) toward the first position; and a switch housed with the pass through opening (56, 86) of the cylinder lock monitor housing (34, 72), fixed or integral with the plunger (36, 74), the switch being in electrical communication with an indicator and adapted to be reactive to any change in position of rotating cam of the cylinder lock wherein the inner portion of the plunger (36, 74) is adapted to contact the rotating cam between and including the first and second positions of the plunger (36,74).