Ferrell was born John William Ferrell in Irvine, California, the son of Kay (née Overman), a teacher, and Lee Ferrell, a keyboardist for The Righteous Brothers. He attended University High School in Irvine CA, and was a kicker for the school's varsity football team.[4] He enrolled at the University of Southern California, where he studied Sports Broadcasting and graduated with a degree in Sports Information. He is also a member of Delta Tau Delta Fraternity. After graduating in 1990, Ferrell developed his improvisation skills as a member of the comedy group The Groundlings. He was shown in his 7th grade yearbook at Rancho San Joaquin Intermediate School as "John Ferrell" (1980). The yearbook reflects that he made the Principal's Honor Roll that year, although he does not appear in the corresponding group photo.

In August 2000, Ferrell married Swedish actress Viveca Paulin, whom he met in 1995 at an acting class. On March 7, 2004, their son Magnus Paulin Ferrell was born. On December 30, 2006, Viveca gave birth to another son, Mattias Paulin Ferrell.[19]

In 2006, I-Newswire.com, a site which accepts press releases from users for publication, reported that Ferrell had died in a paragliding accident. The hoax was published before its factual inaccuracy was noticed. The story was further propagated when it appeared on Google News. Ferrell is a fan of USC Trojan football, At USC, Ferrell was a member of Delta Tau Delta fraternity and is now an active alumnus. Ferrell has worked with head coach Pete Carroll to do motivational stunts for the players during the season.[4]

Ferrell enjoys running and has participated in several major marathons such as the Boston, New York and Stockholm Marathons [20]

In 2007 Autograph magazine named Ferrell the worst celebrity autographer. Its editor stated "What's so frustrating about Will Ferrell being the worst autograph signer this past year is that he used to be so nice to fans and collectors, and a great signer. What makes him so bad is that he'll taunt people asking for his autograph."[21] In response, Ferrell has stated "I don't know how I got on the list. I sign a lot of autographs", but has admitted to taunting autograph-seekers: "I do. I really do. I'm like, 'How badly do you want this autograph?' 'Are you sure?' 'You say you're my biggest fan, really, prove it.' I'll do things like that. They have to earn it."[22]

Ferrell has noted that, though he is well known for his SNL impersonation of President George W. Bush, he chose not to meet the President on several occasions, unlike his SNL predecessor Dana Carvey's famous chummy relationship with George Bush Sr., for both professional and political reasons: "I declined, partly out of comedic purposes, because when I was on the show [Saturday Night Live] at the time, it didn't make sense to really meet the people that you play, for fear of them influencing you. And then the other side of it is, from a political standpoint, I don't want to meet that guy."