Crama started his career at French side Beziers before moving to Brentford's development squad in 2020 and since then has attracted a number of loan offers.
One of these loans was last season at Bristol Rovers where he made 27 appearances in League One and impressed Exeter manager Gary Caldwell.
The Frenchman is yet to play a senior game for the Bees but this loan will allow him to showcase his ability and try and earn a place in the side.
Caldwell had a lot of praise for the defender as he makes him his ninth addition of the summer.
"Tristan is someone that I've kept track of."
"He had a fantastic loan last season with Bristol Rovers in this league so he's gained good experience at this level and I believe he's someone who's ready to be a fantastic defender for us this season."