He has also represented the Japan national team, helping them win the bronze medal at the 2013 East Asia Basketball Championship.

On January 31, 2014, in his first appearance in the annual National Prep School Invitational, Watanabe scored 12 points versus Suffield Academy.

"[13] The Colonials had four other recruits coming into the program for 2014–15: Anthony Swan, Darian Bryant, Matt Cimino, and Paul Jorgensen.

"[10] The George Washington athletics website received the second-most views from Japan in hits by country, ranked behind only the U.S. On many occasions, he was congratulated on the school's campus.

[16][17] On December 12, Watanabe was named Atlantic 10 Rookie of the Week after averaging 9.0 points and 4.7 rebounds in three games as he helped the team win the 2014 Diamond Head Classic crown.

[18] Watanabe hit a key three-pointer with 3 minutes and 32 seconds remaining to upset Wichita State with a 60–54 win on December 25.

[23] On March 31, he logged a team-high 19 points and a career-high four blocks as George Washington won the 2016 National Invitation Tournament with a 76–60 win over Valparaiso.

[34] On October 27, 2018, Watanabe made his NBA debut, coming off the bench with two points and two rebounds in a 117–96 win over the Phoenix Suns.

[35] Though he spent the majority of the season in the G League with the Hustle, the Grizzlies were third behind the Los Angeles Lakers and Golden State Warriors in merchandise sold in Japan due to Watanabe's presence.

On December 14, 2019, Watanabe and Rui Hachimura of the Washington Wizards became the first pair of Japanese players to share the court in the NBA.

[39][40] On January 4, 2020, Watanabe had a team-high 28 points on 12-of-19 field goal shooting and 2-of-4 from three, to go with seven rebounds, four blocks, two assists and two steals in the Hustle's 130–127 win over the Iowa Wolves.

[49][50] On December 31, Watanabe debuted for the Toronto Raptors, recording four rebounds, one assist, a block and a steal across nine minutes in a 100–83 win over New York Knicks, notching their first victory of the season.

[51][52] On January 29, 2021, Watanabe scored a then career-high 12 points coming off the bench, along with six rebounds, two assists and two steals in a season-high 24 minutes of action in a 126–124 loss to the Sacramento Kings.

[57][58][59] After missing four games, he returned to action on February 18, logging two rebounds and a block across six minutes of play in a 110–96 win over the Milwaukee Bucks.

[60] On March 4, Watanabe made his first career start against the Detroit Pistons, going scoreless but grabbing four rebounds in 11 minutes of action.

[61][62] On April 10, 2021, Watanabe scored a then career-high 14 points coming off the bench on 6-of-7 field goal shooting and 2-of-2 from three, including a buzzer beater 3-pointer that gave the Raptors a season-high lead in a quarter with 47–26 in the first, to go along with five rebounds, an assist and a steal across 23 minutes of action in a 135–115 win over the Cleveland Cavaliers.

[63][64][65][66] On April 16, Watanabe surpassed his career-high in scoring for the second time in a week with 21 points on 7-of-11 shooting from the field and 2-of-4 from three, along with six rebounds, two assists and one block across 26 minutes in a 113–102 win over the Orlando Magic.

[67][68][69][70] On April 18, Watanabe logged his third consecutive double-digit scoring game with 10 points, shooting 3-for-6 from the field and 1-for-2 from three, in addition to four rebounds and four assists in 29 minutes off the bench in a 112–106 win over the Oklahoma City Thunder.

[76] On December 14, Watanabe logged his first career double-double with 12 points coming off the bench on 5-of-8 field goal shooting and 2-of-4 from three and a then career-high 11 rebounds, to go along with two assists and a steal across 26 minutes of action in a 124–101 win over the Sacramento Kings.

[77] On December 26, Watanabe posted his second double-double with 26 points and 13 rebounds, both career-highs, in a 144–99 loss to the Cleveland Cavaliers.

"[87] Later, while attending Jinsei Gakuen High School, Watanabe was called up by Suzuki to compete with the national team in 2013.

[2] At the age of 18, he made his senior debut for Japan at the 2013 East Asia Basketball Championship, where he helped the team win the bronze medal.

[89] At the 2013 FIBA Asia Championship, he averaged 5.2 points, 1.2 rebounds, and 0.5 assists in four games played,[90] helping the team finish in ninth place.

"[97] In 2019, SB Nation sportswriter Brandon Abraham lauded his defense, saying, "The Grizzlies and Hustle were simply better with Yuta on the court.

[46][96] In addition, Watanabe has been praised for being constantly in motion,[98][100] which helped him to "always be a step ahead of the opposing offence" as noted by Raptors HQ of SB Nation.

[100] Sports Illustrated observed that Watanabe "plays like his feet are on fire," and that he is "constantly running around, jumping in and out of attacking lanes, and wreaking havoc on opposing offences.

George Washington head coach Mike Lonergan said that he hoped that he weighed over 200 pounds by the start of his sophomore season.

"[38] Watanabe supposedly lacked panache at the time he joined the George Washington basketball program, with teammate Kevin Larsen commenting, "We told him to find a new celebration because the one he had wasn't cutting it.