Valdini was an enlisted member of Starfleet in the 23rd century. He was assigned to the USS Enterprise, serving under the command of Captains Christopher Pike and James T. Kirk. In the 2250s, Valdini was was assigned to the sciences division, and was assigned as a functionary on the Enterprise bridge. José Tyler remembered Valdini as the person who stood next to the turbolift door for no other reason than protocol and always had a self-conscious smile.
In 2287, Tyler asked Spock what had ever become of Valdini. Spock replied that Valdini had been killed by the dikironium cloud creature on Argus X in the late 2260s on stardate 3619.2 (in 2268). (TOS novel: The Rift)