The eight-part series, set at the fictional Bridgeford University, follows a group of students as they settle in to a dark new world full of "recreational sex, recreational drugs, and random murder".
Charles Dance, Claire Skinner, Reggie Yates, Antonia Bernath and Isabella Calthorpe have also landed roles in the show.
Former Echo Beach star Cooke will play the spoiled and manipulative Dorian, while Bernath has been cast as Charlotte Arc, a new student whose father is found dead in mysterious circumstances two weeks before she is due start university.
"Hot on the heels of the phenomenal success of Secret Diary Of A Call Girl, Trinity is set to further cement ITV2’s growing reputation as the place to see dynamic, sexy home grown dramas," said ITV2 controller Zai Bennett.
"Breaking a host of gorgeous, up-and-coming new talent alongside great established names, the heightened world of Trinity is a place I’m sure our viewers will want to spend time in."
The series is due to begin in September.