Boston Celtics (2014–2023) Early years (2014–2016) On June 26, 2014, Smart was selected with the sixth overall pick in the
2014 NBA draft by the
Boston Celtics. He joined the Celtics for the
2014 NBA Summer League, and signed with the team on July 10. In just his fifth NBA game, Smart sprained his left ankle during a 101–98 victory over the
Indiana Pacers on November 7. He underwent an MRI following the game and was ruled out for two to three weeks. After missing 10 games with the injury, Smart returned to action on December 3 against the
Detroit Pistons. The next day, he was assigned to the
Maine Red Claws of the
NBA Development League. Smart was recalled the next day after playing in Maine's victory over the
Erie BayHawks. On March 18, 2015, he scored a season-high 25 points in a 122–118 loss to the
Oklahoma City Thunder. Three days later, Smart was suspended for one game without pay for hitting
San Antonio Spurs forward
Matt Bonner in the groin the previous night. On May 18, Smart was named to the NBA's All-Rookie Second Team, garnering 142 points in the voting process. On July 16, 2015, while playing for the Celtics at the
2015 Las Vegas Summer League, Smart dislocated two fingers on his right hand. On November 15, Smart scored a career-high 26 points in a 100–85 victory over the
Oklahoma City Thunder. Between November 22 and December 26, he missed 18 games with a lower left leg injury. Smart returned to action on December 27 against the
New York Knicks, scoring six points in 13 minutes off the bench. On January 15, 2016, in a 117–103 victory over the
Phoenix Suns, he recorded his first career triple-double with 10 points, 11 assists, and 11 rebounds, becoming the first Celtics player to record a triple-double off the bench since
Art Williams did so in 1971. On January 31, Smart tied his career high of 26 points in a 119–114 loss to the
Orlando Magic.
First Eastern Conference Finals appearance (2016–2017) On November 9, 2016, Smart scored a then season-high 20 points in a 118–93 loss to the
Washington Wizards. On December 25, he scored 15 points and made a tie-breaking three-pointer with 47 seconds left to help the Celtics claim a 119–114 victory over the
New York Knicks. On January 7, 2017, Smart scored a season-high 22 points in a 117–108 victory over the
New Orleans Pelicans. During Game 3 of the Eastern Conference Finals against the
Cleveland Cavaliers on May 21, Smart, who started in place of the injured
Isaiah Thomas, made seven three-pointers and scored 27 points to help the Celtics win 111–108. The Celtics were blown out in the first two games of the series and came back from a 21-point deficit in the third quarter of Game 3. Boston went on to lose the series in five games.
Injuries and first All-Defensive selection (2017–2019) On November 27, 2017, Smart scored a season-high 23 points, making 6-of-9 from three-point range, in a 118–108 loss to the
Detroit Pistons. He missed 11 games between January 24 and February 14 after cutting his hand on glass at the team hotel in Los Angeles. On March 16, 2018, Smart was ruled out for the rest of the regular season with a torn ligament in his right thumb. After missing the Celtics' first four games of the playoffs, Smart returned for Game 5 of the first-round series against the
Milwaukee Bucks. He came off the bench and had nine points, five rebounds, four assists, and three blocks in a 92–87 victory, helping the Celtics take a 3–2 lead. On June 29, 2018, the Celtics tendered a qualifying offer to make Smart a
restricted free agent. On July 19, he re-signed with the Celtics to a four-year, $52 million contract. On November 9, Smart had his first double-double of the season with 13 points and a season-high 10 assists in a 123–115 loss to the
Utah Jazz. Smart missed the end of the regular season and the first round of the playoffs with a left
oblique tear. He returned during the second round of the playoffs. Following the season, Smart was named to the
NBA All-Defensive First Team.
Career high in scoring and health problems (2019–2021) On January 18, 2020, Smart dropped a career-high 37 points in a 123–119 loss to the
Phoenix Suns. He went 11 for 22 from three in the game, breaking the Celtics record for three pointers in a single game. On March 20, Smart was tested positive for
COVID-19 after fellow NBA player
Rudy Gobert was tested positive eight days prior, which had caused the NBA season to suspend indefinitely. Smart was one of the first NBA players to speak out publicly regarding the concerns of COVID-19 and how the community should not take the disease lightly. On March 29, he was cleared from COVID-19. After the season, Smart was named to the NBA All-Defensive First Team for the second time. On April 28, 2021, Smart was suspended for one game without pay for directing threatening language towards a game official.
Defensive Player of the Year and NBA Finals (2021–2023) On August 16, 2021, the Celtics re-signed Smart to a four-year, $77 million contract extension. During the summer of 2021, new head coach
Ime Udoka named Smart the team's starting point guard; he remained in that role throughout the season and during the Celtics' 2022 playoff run. On October 14, 2021, he was suspended for the team's final preseason game for missing a team flight to
Florida. As of February 2022, Smart was the longest-tenured member of the Celtics' team. Smart was named the 2021–22
NBA Defensive Player of the Year on April 18, 2022, the first guard to win the award since
Gary Payton won it in 1996. Smart became the fifth guard in NBA history (alongside
Michael Jordan,
Gary Payton,
Sidney Moncrief, and
Alvin Robertson) to win the award. Ten days later in Game 7, he logged 24 points, nine rebounds, five assists, and two steals during a 100–96 victory, advancing to the
NBA Finals for the first time in his career, and the Celtics' first NBA Finals appearance since 2010. On June 2, Smart made his Finals debut against the
Golden State Warriors and finished the 120–108 road victory with 18 points, five rebounds, four assists, and two steals. Six days later in Game 3, Smart had 24 points, seven rebounds, and five assists in the 116–100 victory. The Celtics took a 2–1 series lead, but eventually lost in six games. In the 2023 NBA playoffs, Smart averaged 14.9 points, 4.0 rebounds, 5.1 assists, and 1.3 steals per game. He averaged 34 minutes played per game, shot 45.3% from the field overall, made 36.1% of three-point attempts, and made 80% of free throw attempts. Smart had only 1.9 fouls times per game and turned the ball over 2.3 times per game.
Memphis Grizzlies (2023–2025) On June 22, 2023, Smart was traded to the
Memphis Grizzlies as part of a three-team deal that sent
Kristaps Porziņģis to the Celtics and
Tyus Jones to Washington. The trade also involved the Grizzlies sending a 2023 first-round pick (pick No. 25) and a top-four-protected 2024 first-round pick (via
Golden State Warriors) to the Celtics. Additionally, the
Washington Wizards acquired
Danilo Gallinari,
Mike Muscala, and Boston's 2023 second-round pick (pick No. 35). On October 25, 2023, Smart made his Grizzlies debut, recording up 17 points, three assists, and two steals in a 111–104 loss to the
New Orleans Pelicans. At the 2024 NBA All-Star break, Smart averaged a career best 14.4 points alongside 2.0 steals while playing 30.2 minutes per game. However, he only appeared in 20 games during the
2023–24 season due to injuries. Smart played in just one game following the All-Star break, a 121–118 overtime loss to the
Sacramento Kings on March 18, where he played just five minutes without recording a single stat in any category.
Washington Wizards (2025) On February 6, 2025, Smart was traded to the
Washington Wizards along with
Colby Jones and
Alex Len for
Johnny Davis,
Marvin Bagley III, and a 2025 second-round pick in a three-team trade that sent
Jake LaRavia to the
Sacramento Kings. On July 20, Smart was waived by the Wizards after a contract buyout agreement.
Los Angeles Lakers (2025–present) On July 22, 2025, Smart signed a two-year, $11 million deal with the
Los Angeles Lakers. In December 2025, he was fined $35,000 for making an obscene gesture towards a game official at halftime during a game against the
Utah Jazz. In a game three playoff game against the
Houston Rockets on April 24, 2026, Smart put up what was described as a strong defensive performance, recording 21 points and 10 assists. ==Player profile==