Ben was a golden retriever who gained fame for regularly accompanying Herbstreit to games and even appearing on set and the sideline.
Herbstreit, who calls college football on ESPN and NFL games on Amazon Prime Video, posted on X that cancer had spread through his dog's organs and "there was nothing left we could do — we had to let him go."
The 55-year-old former Ohio State quarterback said he's had dogs his whole life but "Ben was 1 on 1."
Ben last traveled to Bloomington, Indiana, for the Hoosiers' game against Washington on Oct. 26. His friendliness and frolicking made him a favorite with players, coaches and fans, and condolences poured in online.
Herbstreit told The Associated Press last year that Ben provided a piece of home on the road.
"Just having him come out with me is the best companion you can hope for. He's super chill and welcoming," Herbstreit said before an NFL game last December in Las Vegas. "What's cool is taking him to the games. Both production groups have got to know him. He's really become part of the team. If I don't bring him to the meetings, people ask."