The 2018–19 Dallas Mavericks season was the 39th season of the franchise in the National Basketball Association (NBA). With an overtime loss to the New Orleans Pelicans on March 18, the Mavericks would once again have a losing season and not make the playoffs for the third consecutive year.
 It was Dirk Nowitzki's 21st and final season with the Mavericks, making his season debut on December 13, 2018 against the Phoenix Suns. Not only would he break a record previously set by Kobe Bryant for the most seasons spent playing for a single NBA team, but he also became the fifth player in the NBA history to play in the league for 21 seasons. Believed by many as the greatest Maverick of all time, Nowitzki led the Mavs to 15 playoff appearances (2001-2012; 2014-2016), to a Finals appearance in 2006, and to their first championship title in 2011, defeating the Big 3-led Miami Heat. A 14-time NBA All-Star, Nowitzki is the first European player to start in an All-Star Game, and the first to win the MVP Award. He is also the highest scoring foreign-born player in NBA history and on March 18, 2019, became the 6th highest scoring player of all time, surpassing Wilt Chamberlain's 31,419 points. Nowitzki's retirement leaves former Maverick and fellow 1998 draftee Vince Carter (who played for the Atlanta Hawks) as the last remaining active player to have played in the 1990s. Additionally, Carter became the first player to play in 4 different decades after retiring the following season, a record that Nowitzki could have possibly achieved prior to announcing his retirement on April 9, 2019.
 On January 31, 2019, the Mavericks acquired NBA All-Star Kristaps Porziņģis in exchange for Wesley Matthews and former no. 9 overall pick Dennis Smith Jr.
 This was the last time that the Mavericks missed the playoffs until 2023.
 Entering the night of the draft, the Mavericks originally held only the fifth, thirty-third, and fifty-fourth picks of the 2018 NBA draft. The last of their second round picks was acquired from a three-way trade the previous season from the Denver Nuggets that also involved the New York Knicks. The Mavericks originally fell down a spot from fourth to fifth during the NBA Draft Lottery due to them originally missing out on the Top 3 selections, despite having the tiebreaker over the Atlanta Hawks for better odds there. This also resulted in them having the better second round pick over the Hawks by comparison. Ironically, by the night of the draft, Dallas traded their original first-round pick in the draft (which became Oklahoma Sooners point guard Trae Young) and a protected 2019 first-round pick to Atlanta in exchange for the Hawks' own first-round pick, which became the Slovenian superstar guard/forward Luka Dončić. Dončić is a combo guard/small forward that grew to be a very major contributor for Real Madrid Baloncesto in the EuroLeague and Spain's national Liga ACB, winning championships and MVP awards throughout his professional tenure there, including being named the youngest ever EuroLeague Final Four MVP that year.
 During the beginning of the second round, the Mavericks selected point guard Jalen Brunson from Villanova University. Brunson was a key contributor for two out of three years of NCAA Championships during his time at Villanova, with his second championship year (final college year overall) also naming him both the consensus National College Player of the Year and All-American First Team member. Finally, with their last (54th) pick, they traded that selection (which became Southern Methodist University point guard Shake Milton) to the Philadelphia 76ers in exchange for their last two second round picks this year. With pick #57, the Mavericks received power forward Ray Spalding from Louisville University, while the very last selection of the 2018 NBA draft became combo forward Kostas Antetokounmpo, younger brother of superstar Giannis Antetokounmpo, from Dayton University. Antetokounmpo later signed a two-way contract to stay with the team on July 13, 2018.
 Roster  Last transaction: 2019–04–10
 The preseason scheduled was announced on August 23, 2018.
 The schedule was announced on August 10, 2018.
 
 After all games.
 ‡Waived during the season
†Traded during the season
≠Acquired during the season