Krasinski's first stage experience was starring in a satirical play written and cast by B. J. Novak for Newton South High School. He decided to continue acting after doing a reading of David Foster Wallace's Brief Interviews with Hideous Men. Besides training at the National Theatre Institute, he also studied at The Royal Shakespeare Company in Stratford-upon-Avon and The Actor's Center in New York City. After graduating from Brown University, Krasinski went to New York City to pursue acting, doing commercials and guest spots on television shows, but also doing readings of off-Broadway plays and working as a waiter[citation needed]. He also starred in the play "What the Eunuch Saw", directed and written by a former college classmate.

Krasinski spent the summer of 2000 as a script intern on Late Night with Conan O'Brien.In addition to his role on The Office, Krasinski's television credits include appearances on Law & Order: Criminal Intent, Without A Trace, Ed, American Dad