Early years Lessort was handed his first professional contract by the club in June 2014 and made his debut in the French top-flight
Pro A during the 2014–15 season. Before turning professional, he had considered enrolling at a university in the United States and had been in touch with
Gonzaga and
North Carolina State. He saw action in 23 games as a rookie, chipping in with 2.0 points a game, while pulling down 2.0 rebounds per contest. In 2015–16, he logged his first minutes in a European club competition, the
FIBA Europe Cup. In April 2016, he declared for the
NBA draft, but later withdrew. On 1 June 2016 he joined
JSF Nanterre of the French
Pro A on a three-year deal. In April 2017, Lessort won both the
French Basketball Cup and the
FIBA Europe Cup championships with Nanterre. On 11 August 2017 Lessort signed a three-year deal with the Serbian club
Crvena zvezda. He played there only in the
2017–18 season, before signing with Spanish ACB side
Unicaja in July 2018. Lessort spent the 2019–20 season in Germany with
Bayern Munich.
AS Monaco (2020–2021) On 18 September 2020, Lessort signed with
AS Monaco of the French
LNB Pro A.
Maccabi Tel Aviv (2021) On 25 September 2021, Lessort signed a 2-month contract with
Maccabi Tel Aviv of the
Israeli Premier League in order to replace the injured
Ante Žižić. In five games, Lessort averaged 7.4 points and 3.4 rebounds per game. He parted ways with the team on 26 November.
Partizan Belgrade (2021–2023) On 20 December 2021, Lessort signed with
KK Partizan of the
Basketball League of Serbia, the
ABA League and the
EuroCup. On 18 July 2022, he signed a new contract with Partizan. Under coach Željko Obradović. He was one of the most useful players in the Euroleague, he was in the first team of the Euroleague, and he was also one of the main candidates for the MVP title. During the 2022–23 season, Partizan was eliminated from the
Real Madrid in tight
playoffs series. Over the season, Lessort averaged 12 points and 7.1 rebounds per game. Partizan ended the 2022–23 season by lifting the
ABA League championship trophy, after 3–2 score against Crvena zvezda in the Finals series. In March 2023, Lessort was involved in a physical altercation after an
ABA League derby between
Partizan and
Crvena zvezda, following provocation by
Filip Petrusev. In the moments after full-time, Lessort shoved Petrusev and then struck him in the face. He later apologized for his reaction, saying he felt his dignity had been impinged. He was suspended for three games and fined €10,000 for the incident.
Panathinaikos (2023–present) On 27 June 2023, Lessort signed a two-year contract with Greek powerhouse
Panathinaikos. On February 29, 2024, in a 97–86 win against
Real Madrid, Lessort set his
EuroLeague career-high of 26 points, alongside 7 rebounds and 4 assists. On May 26, 2024, Lessort helped Panathinaikos win its seventh EuroLeague title by scoring 17 points and recording 6 rebounds in a 95–80 win over Real Madrid in the final. On December 19, 2024, during a EuroLeague match against
Baskonia, Lessort suffered a serious fibula fracture in his left leg. The injury caused panic inside the arena, with several fans fainting and one suffering a heart attack. He underwent successful surgery the following day at
Ygeia Hospital, performed by team physician Dr. Athanasios Konidis. Initial estimates suggested an absence of approximately four months. On December 31, 2024, and whilst being injured, Lessort officially signed the newly offered three-year contract extension with the defending EuroLeague champions through 2028. Despite the severity of the injury, Lessort began rehabilitation quickly and made a surprising return during the
2025 EuroLeague Final Four in
Abu Dhabi, where he logged minutes in the semifinal against
Fenerbahçe Beko. However, he was later omitted from Panathinaikos’s roster for the
domestic league finals against
Olympiacos. Team doctor Thanasis Konidis stated that Lessort had been medically cleared to play, but the coaching staff opted to rest him to allow confidence and rhythm to return gradually rather than due to any renewed medical restriction. On 29 September 2025, Panathinaikos head coach
Ergin Ataman provided an update on Lessort’s recovery from his serious fibula fracture. Ataman confirmed that while Lessort was progressing, he was not yet ready to return to full team activities. The club intended to act cautiously, and Lessort was expected to be available for selection in November. Ataman stressed that Lessort’s participation in the EuroLeague Final Four was not a misjudgment, noting that the player had completed one month of intensive individual and partial team training prior to the tournament. “He’ll return in November, about 1–1.5 months from now,” Ataman said. However, on 7 November 2025, the club issued a further statement indicating that Lessort’s recovery plan remained unclear. During his reintegration phase he experienced discomfort in his left ankle, and new imaging revealed bone oedema, prompting a reassessment of his treatment strategy. The statement noted that a decision was yet to be made regarding whether he would continue with conservative treatment or undergo surgery. As a result, no definitive timetable for his return to full team participation was given. On 17 November 2025, Panathinaikos and head coach
Ergin Ataman provided an update on Lessort’s recovery. They confirmed that he had been experiencing persistent discomfort in his left ankle and that new imaging revealed bone oedema. The club stated that a final decision on whether to continue with conservative treatment or proceed with surgery was still pending, and no definitive timetable for his return to full team participation was given. He eventually returned to action on March 12th in a home game against Zalgiris Kaunas, recording 9 points and 3 rebounds in 23 minutes of play.
NBA draft rights Lessort was drafted in the second round as the 50th pick in the
2017 NBA draft by the
Philadelphia 76ers. In July 2019, his draft rights were traded to the
Los Angeles Clippers as part of a four-team trade. On 19 November 2020 his draft rights were traded to the
Minnesota Timberwolves. Lessort's draft rights were traded again, to the
New York Knicks, on 20 November. On February 6, 2025, Lessort's draft rights were included in a four-team trade and ultimately acquired by the
Milwaukee Bucks. ==National team career==