A manhole security cover includes a manhole cover body comprising a non-metallic RF signal transmissive material. The manhole cover body is seatable on a manhole frame to cover a manhole opening. In the seated position, the first side is accessible from outside the manhole, the second side is disposed within the manhole, and the peripheral edge portion engages a manhole cover support surface on the manhole frame. A manhole cover tamper sensor is responsive to a predetermined movement of the manhole security cover body. A transmitter is operatively connected to the manhole cover tamper sensor and configured to generate a radio frequency manhole cover tamper signal when the manhole cover tamper sensor detects the predetermined movement of the manhole security cover body. An antenna is operatively coupled to the transmitter to radiate radio frequency energy through the manhole cover body to a receiver located outside of said manhole.