He also had a recurring role as Jake Jagielski in the WB series One Tree Hill and as Nick Garrett on the ABC drama October Road.

At age 12, Greenberg and his family moved to St. Louis, Missouri, where he got his first major role in a nationally-broadcast Cookie Crisp cereal commercial.

After landing small roles on several TV series (Boston Public, The Sopranos, and Third Watch among others), Greenberg was cast as Matty Matthews, a high school student trying to pass the SAT exam, in the film The Perfect Score.

[2] While he was still appearing in One Tree Hill, he began shooting another television show produced by George Clooney for HBO called Unscripted.

[11] The Washington Post called it "The New Yorkiest thing you could find on television, which is saying something," and praised its "portrayal of a dirty, scrappy, multi-ethnic New York culture.

That same year, Greenberg starred in the dark comedy film The Normals, which follows a young man who enters a two-week clinical trial of an anti-psychotic treatment at a drug-testing center in Queens.

At his New York City Show at the High Line Ballroom, Greenberg was joined by How to Make it in America co-star Kid Cudi.

Greenberg's songs have been featured in many of his film and television work, including One Tree Hill, October Road, and Nobel Son.

In 2011, Greenberg released his second album, We Don't Have Forever, produced by Thom Monahan (Vetiver, Devendra Banhart, Gary Louris), which included the single "Walk Away".