During the early stages of his career, Gleeson directed and wrote several short films, garnered a Tony Award nomination in 2006 for his role in the Broadway production The Lieutenant of Inishmore, and had a supporting role in Never Let Me Go.
Tijekom ranog razdoblja karijere, Gleeson je režirao i napisao nekoliko kratkih igranih filmova, zaradio nominaciju za nagradu Tony 2006. godine za ulogu u broadwayjskoj produkciji The Lieutenant of Inishmore te ostvario sporednu ulogu u filmu Nikad me ne ostavljaj.