The 1988–89 Dallas Mavericks season was the ninth season for the Dallas Mavericks in the National Basketball Association. During the off-season, the team signed free agent Terry Tyler. After reaching the Conference Finals last year, the Mavericks got off to a fast start by winning nine of their first twelve games of the regular season. However, after a 17–9 start to the season, the team posted a seven-game losing streak in January, and later on held a 24–21 record at the All-Star break. In January, sixth man Roy Tarpley was suspended indefinitely for violating the league's anti-drug policy; Tarpley was also out with a knee injury, only playing just 19 games.