Dončić made his regular-season debut on October 17, 2018, recording 10 points, 8 rebounds, and 4 assists, in a 121–100 loss to the Phoenix Suns. On October 20, Dončić recorded 26 points and 6 rebounds in a 140–136 win over the Minnesota Timberwolves. He became the youngest 20-point scorer in franchise history. On October 29, Dončić posted 31 points and 8 rebounds in a 113–108 loss to the San Antonio Spurs, for his first 30-point game in the NBA. He recorded his first NBA double-double on November 19, with 15 points and 10 rebounds in a 98–88 loss to the Memphis Grizzlies. Dončić was named NBA Rookie of the Month in the Western Conference for November 2018. On December 8, Dončić scored 21 points in a 107–104 win over the Houston Rockets. After initial struggles, he produced a personal 11–0 run in the game's final minutes. On December 28, Dončić scored 34 points and became the youngest NBA player to make seven three-pointers in a game. He was named Western Conference Rookie of the Month for December 2018. On January 21, Dončić recorded his first NBA triple-double with 18 points, 11 rebounds, and 10 assists in a 116–106 loss to the Milwaukee Bucks, which made him the third-youngest player in NBA history to accomplish the feat at 19 years and 327 days old, behind LaMelo Ball and Markelle Fultz. On January 27, Dončić scored a season-high 35 points and recorded his second NBA triple-double adding 12 rebounds and 10 assists in a 123–120 loss to the Toronto Raptors. He became the first teenager in NBA history with a 30-point triple-double and with multiple triple-doubles. Two days later, Dončić was named a confirmed participant for the World Team in the 2019 Rising Stars Challenge. Despite being second in fan voting, behind only LeBron James, and ranked 8th in the total voting score, Dončić wasn't selected for the Western Conference All-Stars in the 2019 NBA All-Star Game.