McDorman was born John Allen McDorman IV in Dallas, Texas to John Allen McDorman III and Deborah Gale Stallings; he has a younger sister, Morgan, and an older half-sister, Mandy. After dropping out of the Boy Scouts of America to pursue his acting career, he booked his first job playing a Boy Scout in an industrial film about the importance of Scouting. McDorman studied acting at the Dallas Young Actors Studio and attended Richardson High School in Texas.

In 2004, he starred in the series, Quintuplets, playing Parker Chase, one of the quintuplets. After the show ended, he starred in the film Echoes of Innocence and recently appeared in the films Aquamarine, where he plays a lifeguard falling in love with a mermaid, and Bring It On: All or Nothing, where he played Hayden Panettiere's boyfriend.

He's recently guest starred in the shows CSI: Miami, House, and Cold Case, and is slated to be the lead in the upcoming Greek on ABC Family.