MacGinty was born in Dublin but moved to the US in 2011 and qualified to play for his adopted nation through residency rules.
He has scored 369 points in 56 appearances for the Bears since joining from Sale Sharks in 2022.
Bristol director of rugby, Pat Lam, added: “AJ has been outstanding both on and off the field since joining the Bears, and we’re thrilled to have him remain with the club for another season.
“He’s faced a challenging period with injury this year, but his leadership, professionalism and commitment to the group have been exceptional throughout.”
Academy hooker Tomas Gwilliam has also committed his future to Bristol Bears, signing a new deal of an undisclosed length.
The 23-year-old has made 15 first-team appearances, scoring four tries.
