Astin was a familiar face to TV audiences by the time Steven Spielberg handpicked him to star in The Goonies (1985). Since then, Astin has moved to adult roles in films such as Encino Man (1992), Rudy (1993) and The Low Life (1995). In 1999, Astin gained 30 pounds to land the role of hobbit Sam Gamgee in Peter Jackson's adaptation of The Lord of the Rings trilogy.
Astin also writes, directs and produces films for his company, Lava Entertainment, and in 1995, his second short film, Kangaroo Court, received an Oscar nomination for Best Short Film.