Cleveland Cavaliers (2011–2020) 2011–12 season: Rookie season On June 23, 2011, Thompson was drafted fourth overall in the
2011 NBA draft by the
Cleveland Cavaliers. At the time, he was the highest drafted Canadian-born player in NBA history, that was until
Anthony Bennett and
Andrew Wiggins were selected as the first overall pick in
2013 and
2014, respectively. Thompson continued to make history, drafted alongside Joseph, who was picked 29th by the
San Antonio Spurs, only the second occasion in NBA history to that date that two Canadians were selected in the first round of the same draft, the first being in 1983 when
Leo Rautins and
Stewart Granger were selected 17th and 25th respectively. The 2011 draft was also the first time three Texas Longhorn basketball players went in the first round of a draft, when Thompson's former collegiate teammate
Jordan Hamilton went 26th overall to the
Dallas Mavericks. During the
2011 NBA lockout, Thompson attended classes at the University of Texas to finish his college degree. Thompson signed his rookie contract with the Cavaliers on December 9, 2011, before the start of training camp. Thompson made his professional debut against his hometown
Toronto Raptors on December 26, 2011. In 17 minutes off the bench, Thompson scored 12 points and pulled in 5 rebounds. Both Thompson and teammate
Kyrie Irving were later named to the 2012 Rising Stars Challenge. However, Thompson was selected to play for Team
Shaq, while Irving was selected by Team
Chuck. Thompson finished the season with averages of 8.2 points and 6.5 rebounds in 60 games as he earned
NBA All-Rookie Second Team honors, becoming the first Canadian to ever earn All-Rookie team honors in the NBA.
2012–13 season In the
2012–13 season, Thompson worked on avoiding getting his own shots blocked, and switched his shooting hand from left to right. For most of the season, almost 17%, or one out of six, of his shots were blocked, threatening former NBA player
Danny Fortson's 16.7% rate in
1997–98. Thompson dropped to around 15% by season's end, which was only reached by three other players before the season. He went on to average 3.7 offensive rebounds per game, which ranked fifth in the NBA and first among second year players, and set the Cavaliers franchise record for most offensive rebounds in a single season with 306 (second in the NBA), surpassing
Zydrunas Ilgauskas' 299 offensive rebounds in the 2004–05 season. He also recorded a team-high 31 double-doubles on the season, becoming just the ninth player in franchise history to total at least 30 double-doubles in a single season. He started all 82 games in 2012–13 as he averaged 11.7 points on .488 shooting, 9.4 rebounds and 0.9 blocks in 31.3 minutes per game.
2013–14 season In the 2013 off-season, Thompson decided to switch his shooting hand to his right instead of his left. Despite the change, he had an almost identical season for the Cavaliers in 2013–14, as he started all 82 games while averaging 11.7 points and 9.2 rebounds in 31.6 minutes per game. He tied for fifth in the Eastern Conference with a team-leading and career-best 36 double-doubles.
2015–16 season: Championship season On October 22, 2015, Thompson re-signed with the Cavaliers on a five-year, $82 million contract, ending a four-month contract stalemate that caused Thompson to miss training camp, the preseason, and the
FIBA Americas Championship. Throughout the 2015–16 season, Thompson shared the starting centre role with
Timofey Mozgov. On January 25, 2016, he recorded a season-high 19 points and 12 rebounds in a 114–107 win over the Minnesota Timberwolves. On March 26, in a win over the New York Knicks, Thompson tied
Jim Chones' franchise record by appearing in his 361st consecutive game for the Cavaliers. He broke that record three days later, appearing in his 362nd consecutive game in a loss to the Houston Rockets. Thompson helped the Cavaliers reach the
NBA Finals for the second consecutive season. There they made NBA history by coming back from a 3–1 deficit against the
Golden State Warriors to win the series in seven games, ending a 52-year championship drought in Cleveland.
2016–17 season On December 26, 2016, in a loss to the
Detroit Pistons, Thompson became the first player in franchise history to play in 400 consecutive regular-season games. On April 5, 2017, Thompson missed the Cavaliers' game against the
Boston Celtics with a sprained right thumb. Thompson's absence ended his streak of consecutive games played at 447—the longest in team history and the longest active streak in the league at the time. He missed four games with the injury before returning to action in Cleveland's regular-season finale on April 12 against the
Toronto Raptors. Thompson helped the Cavaliers go 12–1 over the first three rounds of the playoffs to reach the NBA Finals for a third straight season. There the Cavaliers matched-up with the
Golden State Warriors, but lost the
series in five games.
2017–18 season On November 2, 2017, Thompson was ruled out for three to four weeks with a left calf strain that he suffered the previous night against the
Indiana Pacers. On December 12, 2017, he played in his first game since November 1; he went scoreless and did not have a rebound in 6 minutes against the
Atlanta Hawks. On February 25, 2018, he had a season-high 13 rebounds in 23 minutes in a 110–94 loss to the
San Antonio Spurs. In Game 7 of the Cavaliers' first-round playoff series against the Pacers, Thompson, who played just 24 minutes in the first six games, made a rare start and had 15 points and 10 rebounds in a 105–101 win. The Cavaliers made it to the
2018 NBA Finals, where they were swept by the
Golden State Warriors.
2018–19 season To begin the season for the 6–21 Cavaliers, Thompson was averaging career highs in points (12.0) and rebounds (11.6) through 27 games. However, on December 11, he was ruled out for two to four weeks with a left foot sprain. He returned to action on January 2 against the
Miami Heat after missing 10 games. On March 20, against the
Milwaukee Bucks, Thompson returned after missing 26 games with a sore left foot.
2019–20 season On January 9, 2020, Thompson scored a career-high 35 points with 14 rebounds in a 115–112 overtime win over the
Detroit Pistons. He produced a career-best 12.0 points (51.2% FG), 10.1 rebounds, 2.1 assists, 0.9 blocked shots, and 30.2 minutes in 57 games played (51 starts) with the Cavaliers in
2019–20. He was one of six forwards to average a double-double on at least 50.0% shooting in 2019–20, and the only one of that group to also contribute at least 4.0 offensive boards per contest. In 54 games for the Celtics in the 2020–21 season, he averaged 7.6 points and 8.1 rebounds per game.
Sacramento Kings (2021–2022) On August 7, 2021, Thompson was traded to the
Sacramento Kings in a three-team trade involving the
Atlanta Hawks. He appeared in 30 games for the Kings over the first half of the 2021–22 season, averaging a career high 3-point percentage at 1.000%; as well as 6.2 points and 5.4 rebounds per game.
Indiana Pacers (2022) On February 8, 2022, Thompson,
Tyrese Haliburton, and
Buddy Hield were traded to the
Indiana Pacers in exchange for
Justin Holiday,
Jeremy Lamb,
Domantas Sabonis, and a 2023 second-round pick. On February 16, Thompson recorded a season-high 17 points along with 6 rebounds and a block in a win over the
Washington Wizards. On February 17, after playing four games, the Pacers reached a mutual contract buyout agreement with Thompson.
Chicago Bulls (2022) On February 19, 2022, Thompson signed with the
Chicago Bulls. He played in 23 games for the Bulls to finish the 2021–22 season.
Los Angeles Lakers (2023) On April 9, 2023, Thompson signed with the
Los Angeles Lakers ahead of the
2023 NBA playoffs, reuniting with former Cavs teammate
LeBron James. He played in six games for the Lakers during the playoffs, including the May 22, 2023 game where Thompson would
dunk the ball with the assist coming from James in a 113–111 loss in the
2023 Conference Finals. This would be Thompson's last game as a Laker.
Return to Cleveland (2023–2025) On September 12, 2023, Thompson signed with the
Cleveland Cavaliers on a one-year contract. On January 23, 2024, he was suspended for 25 games without pay after testing positive for
ibutamoren and
SARM LGD-4033. Thomson would end the season going .608% from the field; a career high.
2024-25 season On September 9, 2024, Thompson re-signed with the Cavaliers. In the February 13, 2025 game against the
Toronto Raptors, Thompson would come off the bench with four seconds left in the game before proceeding to
dunk the basketball, causing an on-court argument. The Cavaliers would go on to win 131–108. Thompson would go on to finish the season averaging 1.7 points per game, 3.4 rebounds per game, and 8.2 minutes per game; all career lows. ==Career statistics==