The story follows Stan Ross (Bernie Mac) who was a Milwaukee Brewers baseball star with 3,000 hits that earned him the nickname "Mr. 3000." After recording what is believed to be his 3000th hit, the selfish and arrogant Ross retires and leaves the Brewers, leaving the team without one of their star players in the middle of the 1995 playoff race. However, nine years later, it is discovered that (due to a clerical error) he is three hits short of that total, so a 47-year-old Ross returns to the game to get three more hits and secure his place in the record books and keep his local post-career marketing gimmick from being invalid, making for a hostile environment when he returns. But the Brewers' upper management, citing the large attendance at Ross' number retirement ceremony and the fact that the Brewers are out of playoff contention, agrees to bring Ross back during the September roster expansion. The Brewers' younger players only know Ross as the self-centered player that he was before and T-Rex (Brian J. White), the pompous star of their current roster, thinks of Ross as a washed up has-been and feels the team does not need him. Manager Gus Panas (Paul Sorvino) refuses to talk to Ross because of the bad blood left between the two after Ross' first retirement, and the sportswriters make him an easy target for criticism.
Ross struggles to regain his baseball form despite his predictions to the contrary. Eventually, he connects with two more hits, bringing his total to 2,999. In the process, Ross becomes a mentor to the younger players on the team and urges T-Rex to learn from Ross' mistakes in his early days as a hot baseball player, inspiring them from a late-season comeback to a respectable finish. In his last at-bat of the season, Ross gives up a chance at hit number 3,000 so the team can finish 3rd in its division. Although Ross never gets 3,000 hits, he is ultimately inducted into the Baseball Hall of Fame. At the end of the movie he gives in and does a Viagra endorsement commercial. He also ends up with Mo (Angela Bassett).
As the movie ends, Stan alters all the titles on his businesses that bear the name Mr. 3,000 to Mr. 2,999.