As a featured player on Saturday Night Live during the 2004-2005 season, his first appearance as a castmember was on the show's thirtieth season premiere on October 2, 2004. He has portrayed Larry the Cable Guy, Howard Dean, Rick Sanchez, Mark McGwire, and Toby Keith. Before Riggle was hired as a cast member, he appeared in a pre-taped season 29 SNL sketch called "Fear Factor, Jr.", playing the father during the "Breakfast in Bed" challenge in which a child must eat the maggots off a plate of Eggs Benedict or his parents will divorce.

In 2006, Riggle guest-starred as a boat captain named Captain Jack on the "Booze Cruise" episode of The Office, and as a politician on Arrested Development. He is also seen in the 2006 film Talladega Nights with Will Ferrell. In September 2006, he joined the cast of The Daily Show to replace the departing Rob Corddry. Riggle made his debut on The Daily Show on September 20, 2006.

Rob Riggle also played the character of Eddie Reynolds in 2004's Blackballed: The Bobby Dukes Story, a film starring former Daily Show correspondent Rob Corddry as the main character. A Major in the United States Marine Corps Reserve, Riggle, has served in Liberia, Kosovo, and Afghanistan, and is currently a public affairs officer.