There had been previous university-wide groups, such as CAMNUS (Cambridge NUS), which was founded in 1964 by Gordon Heald, John Bibby and others.

Following a referendum of members of CUSU and the University of Cambridge Graduate Union in 2019, the two agreed to merge.

The full-time officers take a one-year sabbatical from their studies (or directly after they have graduated) and are: Cambridge SU is unusual in having 8 full time sabbatical roles, with this number placing it at the highest end of all UK students' unions in terms of number of full-time, elected officers.

[4] Trinity College Students' Union reaffiliated in early 2007, following re-engagement work by the incumbent sabbatical officers.

[6] In 2015 the university had to give CUSU a £100,000 bailout, but incumbent president Priscilla Mensah denied that this was due to financial mismanagement.

[7][8] In 2019, CUSU presented a surplus budget, ending what the Union described as “a few difficult years in recent history” with regards to its financial situation.