The 46-year-old, who won gold medals at the 2000 and 2004 Olympic Games, will ride in the Cambridge boat in the classic race on April 7.
The veteran, almost 25 years older than some of his team-mates, is studying for a philosophy degree at Cambridge, having also been offered a place at Oxford University.
Cracknell has not raced in high-level rowing since 2006 but has taken part in a number of endurance challenges since then and ran a sub-three-hour marathon in 2017.
He is eight years older than the previous oldest competitor Andy Probert, who was 38 when he coxed for Cambridge in 1992.
Cambridge took a clean sweep in races in 2018 and coach Rob Baker says there has been no issue with integrating Cracknell into the team.
He said: "The guys have adapted to it, we haven't had problems in that sense, we have got a clear group of people who are committed and want to work together."