Bartha was born in Fort Lauderdale, Florida, and moved to West Bloomfield, Michigan when he was eight. His father, Stephen, is a real estate developer, while his mother, Betty, is a school teacher. He has one brother, Jeffrey. Bartha's family is Jewish, and he had a "fairly Reformed" upbringing. Bartha attended Camp Walden in Cheboygan, Michigan for 5 years as a child. After he graduated from West Bloomfield High School in 1996, he moved to New York and studied acting at New York University.
Bartha began his film career behind the camera as a production assistant on the film Analyze This. His acting debut came a year later in a short film called Tag in 1999. He wrote and directed a short film, Highs and Lows with Darrell M. Smith as co-producer, which was shown at the South by Southwest Film Festival in 2003. Additionally, he wrote, produced, and starred in an MTV pilot called The Dustin and Justin Show.
Bartha had major roles in the critically bashed Gigli and Carnival Sun in 2003 before his co-starring role in National Treasure (2004) as Riley Poole, which launched him into the mainstream.
In 2006, Bartha had a supporting role in Failure to Launch and starred in the television sitcom Teachers which premiered on March 28, 2006 on NBC (it was cancelled on May 15, 2006 due to low ratings).
