Sean Astin made his feature film debut at age 13 as "Mikey Walsh" in Richard Donner's adventure The Goonies (1984). Sean's portrayal of a young man determined to play football for Notre Dame in Rudy (1993) won hearts across America, and continues to inspire young people whenever it is shown.

Other well-known film credits include Bulworth, Courage Under Fire, Memphis Belle, Encino Man, Like Father Like Son, Where the Day Takes You, Staying Together, War of the Roses, Safe Passage, and White Water Summer.

His role in Peter Jackson's epic film trilogy Lord of The Rings, as "Samwise Gamgee," the trustworthy sidekick of Frodo Baggins (played by Elijah Wood) earned him accolades around the world. He also played the brother of Lucy (Drew Barrymore) in 50 First Dates. Sean received Best Actor honors for his performance in Low Life at the Fort Lauderdale Film Festival.  He can also be seen in the indie releases Deterrence, Kimberly, The Last Producer, Boy Meets Girl, Smile, The Final Season, and Borderland.

A promising director, Astin garnered an Academy Award nomination for his short film Kangaroo Court, which he co-produced with his wife, Christine. A Directors Guild of America member, Astin has also directed episodes of the HBO anthology series Perversions of Science and Angel for The WB.

While working on Lord of The Rings: The Two Towers, he persuaded a number of fellow cast and crew members, including director Peter Jackson, to act in or work as crew on his short film, The Long and Short of It (2003), which takes place on a street in Wellington, New Zealand. The film premiered at the Sundance Film Festival, 2003, and appears on the “standard edition” DVD of The Two Towers as an extra feature together with a “making of” video.

Astin is also the narrator of the US version of Meerkat Manor, shown on the Discovery Channel owned channel Animal Planet. He was the voice of Kodi in the animated film Balto III: Wings of Change.