Born into the Gyllenhaal family, he is the son of director Stephen Gyllenhaal and screenwriter Naomi Foner; his older sister is actress Maggie Gyllenhaal.
He began acting as a child, making his acting debut in City Slickers (1991), followed by roles in his father's films A Dangerous Woman (1993) and Homegrown (1998).
His breakthrough roles were as Homer Hickam in October Sky (1999) and as a psychologically troubled teenager in Donnie Darko (2001).
Aside from acting, he is vocal about political and social issues.
Gyllenhaal's most acclaimed films, according to the review aggregate site Rotten Tomatoes, include October Sky (1999), Donnie Darko (2001), Lovely & Amazing (2002), Brokeback Mountain (2005),
Zodiac (2007), Source Code (2011), End of Watch (2012), Nightcrawler (2014), and Stronger (2017).
He has been nominated for an Academy Award, two Golden Globe Awards, three British Academy Film Awards, and three Screen Actors Guild Awards.