In 2233, three months after the destruction of the USS Kelvin, Keenser became the first Roylan to graduate from Starfleet Academy. For the next 25 years, Keenser was assigned to various ships, starbases and strange new worlds before becoming Chief Engineer of the new research station on Delta Vega.
In 2258, Keenser was given a new engineer at the Starfleet outpost named Montgomery Scott. Scott often belittled and berated Keenser, particularly regarding Keenser's tendency to climb up on things. It was clear that they were fond of each other, however; Keenser, in particular, was saddened when Scott transported with Kirk to the USS Enterprise. Keenser was Scott's only company for months until they encountered James T. Kirk and Spock who had both been marooned on the planet. With Spock's assistance Scott was able to modify the outpost's transporter to function as a transwarp transporter and transport himself and Kirk to the USS Enterprise, leaving Keenser with Spock.
After the Enterprise defeated Nero and the Narada Keenser and Spock were both retrieved from Delta Vega and Keenser joined the Enterprise crew, serving under Scott in engineering.