Tom was born on March 6, 1959 in Ottumwa, Iowa. He attended Indian Hills Community College and the University of Iowa. In the early 1980s, Tom had a prop-based comedy routine called "Tom Arnold and the Goldfish Review." Shortly after moving to Los Angeles to pursue a career in comedy, he was hired as a staff writer for the television show, Roseanne. In addition to writing for the show, he had a recurring role as Arnie Thomas. After the end of Roseanne , Tom went on to have numerous movie roles, including starring alongside Arnold Schwarzenegger in James Cameron's True Lies, and playing Lieutenant Commander Quintin McHale in McHale's Navy. In 2006, Arnold hosted the TV Land Awards "All Access Pass" for TVLand.com. Some of his other television credits include The Jackie Thomas Show, Veronica's Closet, ER, Law & Order: Criminal Intent, and Sons of Anarchy.
Tom currently resides in Beverly Hills, California with his family.