Mario Cardinali was a male Human in Starfleet's First Contact Office in the late 23rd century. During the late 2260s, he was assigned to FCO Outpost 47, serving as manager of communications. As such, he was responsible for the monitoring and analysis of hundreds of audio and visual broadcast signals sent out by the planet under observation, Talin IV.

Following the global nuclear weapon exchange on Talin in 2269, Cardinali and his colleague Carole Mallett left the outpost to rescue two Talin astronauts, Seerl ti'La and Orr ni'Li, who had been stranded off-world. They eventually got the two aboard a Richter Institute starship, and then to Earth. Cardinali later accompanied the Talin back to the outpost, in an effort to determine exactly how and why the nuclear exchange had been triggered. (TOS novel: Prime Directive)