Born in Oregon but raised in Lithuania, Sabonis signed for Spanish club Unicaja Málaga rather than playing in a high school competition and made his debut at the age of 16. He became the youngest player to debut for Unicaja in the Spanish league and proved himself to be a promising young player. In 2013, he finished in the top 10 in the FIBA Europe Young Men’s Player of the Year voting, and in the top 5 in 2014.

In 2014, Sabonis committed to play college basketball for the Gonzaga University Bulldogs. In his debut, he scored 14 points and grabbed eight rebounds. His all-around contributions led to Conference Player of the Week recognition in the West Coast Conference after averaging a double-double in late January. Sabonis ended his freshman season with All-WCC Second Team, WCC All-Freshman team, and NCAA Regional All-Tournament Team honors. The team won the WCC tournament and reached the Elite Eight in the March Madness, losing to eventual champions Duke. 

Entering his sophomore season, Sabonis was rated the 20th-best NCAA player by ESPN. In December, he set college career highs in with 36 points and 16 rebounds against Northern Arizona University. He was named in the 2016 All-WCC First Team before leading Gonzaga to the Sweet Sixteen where they narrowly lost to Syracuse. He easily averaged a double-double in the tournament with 19.6 points and 14.3 rebounds per game. Sabonis was named to the CBS College Basketball All-America Third Team and declared for the NBA draft in the spring of 2016.

In the summer following his draft, Sabonis also represented Lithuania at the 2016 Olympics where he averaged 5.5 points and 4.5 rebounds.

Sabonis participated in pre-draft workouts with the Boston Celtics, Utah Jazz, Toronto Raptors, and Phoenix Suns. He was drafted 11th overall by the Orlando Magic but he, Victor Oladipo, and Ersan Ilyasova were sent to OKC on a draft-night trade for Serge Ibaka.

Sabonis started the Thunder’s season opener, becoming the only player other than Kevin Durant to make a rookie debut for OKC as a starter. He had several strong games as a rookie, including a 20-point game against the Boston Celtics and a 13 point, 13 rebound double-double against San Antonio. At All-Star weekend, he appeared in the NBA Rising Stars Challenge. The Thunder made the playoffs as a six-seed, but Sabonis only featured in two games for a total of six minutes in the postseason.

On July 6, 2017, the Thunder traded Sabonis and Victor Oladipo to the Indiana Pacers for Paul George. In 74 games he averaged 11.6 points and 7.7 rebounds, including a career-high 30 points against the Charlotte Hornets. The team outperformed expectations, with Victor Oladipo emerging as a star and Sabonis working with him as a lethal pick-and-roll duo. Sabonis and the Pacers lost a hard-fought seven-game playoff series against LeBron James and the Cleveland Cavaliers, in which Sabonis posted a playoff career-high of 22 points in game 5.

In his second year as a Pacer, Sabonis’ production continued to grow. In roughly the same number of minutes, he averaged 14.3 points and 9.3 boards per game. While questions emerged about his ability to fit with Myles Turner, the Pacers’ other promising young big man, the team performed well again and Sabonis logged 30 double-doubles. A promising season ended with a disappointing playoff run following Victor Oladipo’s season-ending injury, as the Pacer were swept in the first round by the Boston Celtics.

There was speculation that the Pacers would seek to trade Sabonis in the 2019 offseason, given the difficulties of playing him alongside Myles Turner. Surprisingly many, Indiana signed him to a four year, $77 million extension and Sabonis quickly proved that this was a good decision. Despite missing Oladipo for most of the 2019-2020 season, Indiana played well both with Sabonis partnering Turner as a center/power forward pairing and with Sabonis playing center in their second unit. Sabonis partnered new signing Malcolm Brogdon in a strong pick-and-roll partnership, where he showed off his increased playmaking ability as his assists per game jumped from 2.9 to five. Sabonis became the first Lithuanian basketball player to post a triple-double in the NBA with 22 points, 15 rebounds, and 10 assists in January win against the Denver Nuggets. Despite the season shut down in March, Sabonis had time to record three more triple-doubles and set an Indiana record with 12 consecutive double-doubles. He was selected for the All-Star game where he helped Team LeBron triumph over Team Giannis.