Adam Jared Brody was born and raised in San Diego, California, the son of Valerie Jill (Siefman), a graphic artist, and Mark Alan Brody, a lawyer. His parents, both originally from Michigan, are both from Jewish families (from Russia and Poland). Adam spent a lot of his teen years hanging out with his friends, having fun and surfing. Upon graduation, he convinced his parents to allow him to attend college in Los Angeles. However, instead of enrolling in school, he hired an acting coach, signed with a talent manager and soon landed the lead in the NBC movie-of-the-week, Growing Up Brady (2000), playing Barry Williams (Greg Brady). Soon after, Brody was cast as the lead, Zack Altman, in the MTV series The Sausage Factory (2001). His television credits also include the recurring role of Coop in ABC's Once and Again (1999); a recurring role as Dave Rygalski in The WB's Gilmore Girls (2000); and standout guest-starring roles in Judging Amy (1999), Family Law (1999) and Smallville (2001). Brody then starred in the Fox series The O.C. (2003), portraying Seth Cohen, which made him famous.

In addition to starring in the comedy Grind (2003), Brody's early feature film credits included a minor role in the thriller The Ring (2002), a lead role in the drama Missing Brendan (2003), and supporting roles in the action film Mr. & Mrs. Smith (2005) and the comedy-drama Thank You for Smoking (2005). He then starred in the romantic comedy In the Land of Women (2007) with Kristen Stewart and Meg Ryan, and appeared in the sequel Scream 4 (2011), and the arthouse hit Damsels in Distress (2011). Also in the 2010s, he had memorable roles in the dramedy Seeking a Friend for the End of the World (2012), the superhero comedy Shazam! (2019), and the satirical horror film Ready or Not (2019), the latter two particularly acclaimed films. He began the 2020s with starring in Promising Young Woman (2020), and a bit part in the dark thriller Promising Young Woman (2020), which was nominated for a Best Picture Oscar.