Houston Rockets (2015–2017) On June 25, 2015, Dekker was selected by the
Houston Rockets with the 18th overall pick in the
2015 NBA draft. On July 7, he signed his rookie scale contract with the Rockets but subsequently missed the entire
2015 NBA Summer League due to a back injury. He appeared in all eight of the Rockets' preseason games, but managed game time in just three of the team's first 11 regular-season games. On November 18, 2015, he was ruled out for three months after requiring back surgery. On February 19, 2016, he was assigned to the
Rio Grande Valley Vipers, the Rockets'
D-League affiliate, on a rehab assignment. He was recalled by the Rockets on February 22. He went on to receive two more assignments to the Vipers. On December 14, 2016, Dekker scored a career-high 19 points in a 132–98 win over the
Sacramento Kings. On January 21, 2017, he made his first career start and set a new career high with 30 points in a 119–95 win over the
Memphis Grizzlies.
Los Angeles Clippers (2017–2018) On June 28, 2017, the
Los Angeles Clippers acquired Dekker,
Patrick Beverley,
Montrezl Harrell,
Darrun Hilliard,
DeAndre Liggins,
Lou Williams,
Kyle Wiltjer and a 2018 first-round pick from the Houston Rockets in exchange for
Chris Paul.
Cleveland Cavaliers (2018) On August 7, 2018, Dekker was traded, along with the draft rights to
Renaldas Seibutis and cash considerations, to the
Cleveland Cavaliers in exchange for the draft rights to
Vladimir Veremeenko.
Washington Wizards (2018–2019) On December 7, 2018, Dekker was traded to the
Washington Wizards in a five-player, three-team deal. The Wizards traded
Jason Smith and cash considerations to the
Milwaukee Bucks. The Bucks sent
John Henson,
Matthew Dellavedova, and 2021 first- and second-round picks to the
Cleveland Cavaliers and received
George Hill and a 2021 second-round pick. The Wizards also sent a 2022 second-round pick to the Cavs.
Lokomotiv Kuban (2019–2020) On August 5, 2019, Dekker signed with Russian club
PBC Lokomotiv Kuban of the
VTB United League and the
EuroCup.
Türk Telekom (2020–2021) On July 23, 2020, Dekker signed with
Türk Telekom of the
Turkish Super League (BSL).
Toronto Raptors (2021) On August 10, 2021, Dekker signed with the
Toronto Raptors. However, he was waived on November 6, after making a single regular season appearance.
Bahçeşehir Koleji (2021–2022) On December 4, 2021, Dekker signed with
Bahçeşehir Koleji of the Turkish
Basketball Super League. The team won the 2021-22
FIBA Europe Cup, with Dekker averaging 13.1 points and 7.2 rebounds per game. He helped Bahçeşehir win the
2021–22 FIBA Europe Cup, contributing averages of 11 points and 5.5 rebounds in the
Finals.
London Lions (2022–2024) On August 7, 2022, Dekker signed with the
London Lions of the
British Basketball League (BBL) and the
EuroCup. In his inaugural season, the Lions won both the 2022–23 BBL Cup and Championship, and Dekker was the top scorer in the EuroCup regular season. In May, Dekker was named the MVP of the 2022–23 BBL season. In the
2022-23 Eurocup season, club debut in the second european competition, they reached the play-offs but being knocked in the eightfinals against Joventut Badalona. Sam was the best player of the team in the whole season and play-offs, and got into the
All-Eurocup second team. He won the BBL again in the 2023–24 season, becoming MVP of the Final. In the
2023–24 Eurocup season they reached the semi-finals for the first time in the history of the club but also for an english club in European competitions, being knocked by the future champions of the competition,
Paris Basketball.
Joventut Badalona (2024–2026) On November 12, 2024, Dekker signed a temporary contract with
Joventut Badalona, a historic team from Catalonia (Spain) in the
ACB League. With Joventut finishing in 6th position in the ACB, Dekker averaged 13 points and 4 rebounds per game (41% 3PT). Joventut qualified for the play-offs, falling in the quarterfinals. On August 1, 2025, Sam extended his contract with Joventut Badalona for one more year, until June 2026. In February 2026, Dekker reached an agreement to terminate his contract with Joventut in order to travel to the US to seek treatment for recurring shoulder injuries. ==Personal life==