Fittler has a longtime partner, Marie Liarris. They have two children.<ref>{{Cite news|url=http://www.dailytelegraph.com.au/newslocal/city-east/roosters-legend-brad-fittler-selling-familysize-rushcutters-bay-pad-and-heading-for-greener-pastures/news-story/e9c8aae40755eee95d68194b12e14be0|title = Fittler family selling stylish digs|newspaper = The Daily Telegraph|location=Sydney|date = 3 June 2014|last1 = Melocco|first1 = Jen}}</ref>
He also fathered an illegitimate son after a one-night stand in 1995. He has never met the child and only pays child support, deliberately having chosen not to have seen the boy since 1996.
In an article published written by Sandra Lee in The Sunday Telegraph in 2005, Fittler stated that "I just hope that he lives in a stable environment, that's all I can hope for. I was young ... I just dealt with it as best I could. You don't (come) equipped with those sorts of skills. I suppose I did what I thought was best for me at the time. I just made sure I covered all legal angles, what my commitments were. I was in no state at the time. I didn't think I was up to raising kids. I was 23. I would have asked her to think about it maybe from my point of view. Whether that most probably would have been a selfish point of view ... it's just hard when you're never asked, never confronted. I understand it could be hard on the boy, but the mother has to shoulder much of the blame for the way she went about things." In his autobiography, ''Freddy, The Brad Fittler Story'', Fittler says he believes that a financial contribution to raising his boy, who is now nine, is sufficient.<ref>{{Cite web|title=League: Fittler a secret dad|url=https://www.nzherald.co.nz/sport/league-fittler-a-secret-dad/JTQGEBAJ3NWWTHZVUQ6K2ZGFUU/|url-status=live|website=The New Zealand Herald|archive-url=https://web.archive.org/web/20211001110010/https://www.nzherald.co.nz/sport/league-fittler-a-secret-dad/JTQGEBAJ3NWWTHZVUQ6K2ZGFUU/ |archive-date=1 October 2021 }}</ref><ref>{{Cite web|title=Fittler reveals painful secret| date=21 May 2005 |url=https://www.thegh.com.au/forum/viewtopic.php?t=1717|url-status=live|archive-url=https://web.archive.org/web/20211001110012/https://www.thegh.com.au/forum/viewtopic.php?t=1717 |archive-date=1 October 2021 }}</ref>
In 2022, inducted into [[Sport Australia Hall of Fame Awards|Sport Australia Hall of Fame]].<ref>{{Cite web |date=13 October 2022 |title=2022 SAHOF Inductees & Award Winners |url=https://sahof.org.au/2022-sahof-inductees-award-winners/ |access-date=16 October 2022 |website=Sport Australia Hall of Fame}}</ref>
