He was suffect consul for the nundinium of May to June 55 AD as the colleague of Seneca the Younger, replacing Publius Cornelius Dolabella.
[1] In 61 Trebellius served on a commission to revise the census list and tax assessments in Gaul, together with Quintus Volusius Saturninus and Titus Sextius Africanus.
By 67, the province was secure enough to allow Legio XIV Gemina to be withdrawn, but inactivity, and the lack of opportunities for booty, led to mutinies among the legions that remained.
Not being a military man, Trebellius was unable to restore discipline, and a feud with Marcus Roscius Coelius, commander of XX Valeria Victrix, further undermined his authority.
Instead, Roscius led a mutiny which forced Trebellius to flee, and threw his weight behind Vitellius, sending units from Legio XX to fight for him.