Fittler's first grade career started in 1989 at the Penrith Panthers while he was still in high school. He played in Penrith's 1990 Grand Final loss, then in the Premiership winning side of 1991. In 1996, he joined the Sydney Roosters where he played nine seasons, captaining them to the 2002 Grand Final victory. Fittler is the third most experienced first grader, behind Terry Lamb (349) and Steven Menzies (349), having played 336 games.
Fittler represented the Australian Schoolboys from McCarthy Catholic Senior High School, Emu Plains in 1988 and 1989. He was selected for Kangaroo Tours in 1990, 1994 and 2001 and played in the World Cups of 1992, 1995 and 2000.
Early in his career Fittler struggled with discipline problems, but he matured into a fine leader. He captained Australia in 20 Tests, winning 17 and losing 3, and in a further 5 victories in the 2000 World Cup. He also captained NSW in 14 State of Origin matches, winning 8 and losing 6. In club competition, he captained the Roosters to their first grand final appearance in twenty seasons in 2000, a Premiership in 2002 and successive grand final appearances in 2003 and 2004, before retiring at the end of 2004.
Two years after Fittler announced his retirement from representative football, NSW coach Phil Gould brought him back to State of Origin for the second and third game. Both he and Gould were farewelled in the last game at Telstra Stadium after he scored the winning try that sealed the NSW victory.
Fittler remains the youngest NSW State of Origin player (18 years 114 days) and was once the youngest Kangaroo representative (18 years 247 days) until Israel Folau made his debut in late 2007. Fittler played more total matches (409 combining club and representative games) than any other player.
On 27 July 2007, Fittler's coaching career took a massive leap. The Roosters side defeated the Melbourne Storm [front runners of the Premiership] 26–16, with the two late consolation tries to the Storms misrepresenting the match. Former Roosters coach, Phil Gould remarked after the Melbourne game "I've always had great confidence that "Freddie" would be successful at anything he turned his mind to. If he truly wants to be a coach, he'll be a bloody good one... I think in the end he was drawn to it and, to me, that's a coach. You don't wake up one day and say, 'I want to be a coach'. You are drawn to it. It compels you. I see and hear this in Freddie these days.
Following the win over the Melbourne Storm, the Roosters went up against the New Zealand Warriors with the match resulting in the first draw since 2005 after a hard fought golden point period which ended with the score 31–31. The result was good enough to keep Fittler undefeated as coach.
That run was extended against the Wests Tigers on 10 August, with the second golden point game in a row for the club after a late field goal attempt from Braith Anasta hit the cross bar with 15 seconds to go. The game ended in a 26–22 win after Anasta broke the line and passed to Amos Roberts who then set up Joel Monaghan for the winning try.
Unfortunately, Fittler's winning streak as a coach was broken on the 19 August 2007 when the Roosters played the Gold Coast Titans, losing 22–18. The following week, in the penulitmate round of the regular season, the Roosters lost to the eventual 2007 wooden spooners, the Penrith Panthers, 28–22.
In the final round of the season, the Roosters defeated South Sydney Rabbitohs, 26–12. The game was highly controversial with Souths forward David Fa'alogo king hitting Roosters five-eighth Braith Anasta.
Brad Fittler is also known to be the heart of the Sydney Roosters Outfit. With his influence the Roosters were the most dominant team, finishing in the top 8 every year he was present and often topping the ladder for most of the year. With Brad Fittler absent, The Roosters failed to reach the top 8 for 3 years. With him back in the team as coach they reached the 2008 Finals Series finishing fourth in the regular season.
Fittler has a long time partner, Marie Liarris. They have two children together, a daughter, Demi, and a son, Zach.