The 1998–99 NBA season was the Bucks' 31st season in the National Basketball Association. After a four-month lockout, the Bucks hired head coach George Karl, who previously coached the Seattle SuperSonics, and traded their top draft pick Dirk Nowitzki to the Dallas Mavericks for rookie Robert Traylor, while signing free agents Dell Curry and Vinny Del Negro. The Bucks transition continued at midseason trading Terrell Brandon to the Minnesota Timberwolves, and acquiring Sam Cassell and Chris Gatling from the New Jersey Nets in exchange for Elliot Perry in a three-team trade. In another trade, they dealt Tyrone Hill to the Philadelphia 76ers for second-year forward Tim Thomas and Scott Williams, while signing free agent Haywoode Workman. Under Karl, the Bucks played above .500 for the entire season as they finally entered the playoffs after a seven-year playoff drought, finishing fourth in the Central Division with a 28–22 record.

In the first round of the playoffs, they would be swept by the Indiana Pacers in three straight games. Following the season, Curry signed as a free agent with the Toronto Raptors, Gatling was traded along with Armen Gilliam to the Orlando Magic, who released Gilliam as he signed with the Utah Jazz during the next season, and Michael Curry re-signed with the Detroit Pistons.