2011–12 season

Morris was selected by the Phoenix Suns with the 13th pick in the 2011 NBA draft. His twin brother, Marcus was drafted by the Houston Rockets five minutes later.^[6]

On January 8, 2012, Morris recorded his first professional double-double with 13 points and 10 rebounds in a blowout 109–93 victory over the Milwaukee Bucks.^[7] On January 18, Morris had his first professional start in the NBA against the New York Knicks. However, due to a stomach virus, Morris only played for five minutes, scoring three points and grabbing two steals before Channing Frye took over the power forward position in a 91–88 victory.^[8] On February 8, 2012, Morris was named to the 2012 Rising Stars challenge, making him the first Suns player since Amar'e Stoudemire to appear in the Rookie Challenge.^[9] Morris played for Team Shaq, recording 12 points and six rebounds. On March 25, he recorded a then career-high 22 points to tie Marcin Gortat as the game's leading scorer in a 108–83 victory over the Cleveland Cavaliers.^[10]

2012–13 season

Due to the 2011 NBA lockout, Morris had his first Summer League stint in 2012, where he averaged 19.8 points and 9.8 rebounds per game. After this stint, Morris amassed 13 pounds of muscle while keeping his weight of 245 pounds. After scoring a then season-high 16 points against the defending champion Miami Heat, Morris made his first start of the season on November 21, 2012. Morris topped his season high in points by three and tied Marcin Gortat with seven rebounds in a victory over the Portland Trail Blazers.^[11] Two days later, Morris recorded a then career-high 23 points to lead the Suns to a 111–108 overtime victory over the New Orleans Hornets.^[12] On December 6, 2012, he recorded a career-high 17 rebounds to go along with 15 points in a 97–94 loss to the Dallas Mavericks.^[13]

On February 21, 2013, Morris' twin brother Marcus was traded to the Phoenix Suns, reuniting them after two years of playing for separate teams.^[14] This also marked the second time the Suns had twin brothers playing on the same team, with Dick and Tom Van Arsdale being the first twins to play together during the 1976–77 season. The Morris twins went on to become the first brothers ever to start alongside each other on the same team.

2013–14 season

On November 6, 2013, Morris tied his career-high 23 points and added 12 rebounds in a loss to the San Antonio Spurs.^[15] He went on to post a new career-high two days later, scoring 28 points and grabbing 10 rebounds in a 114–103 victory over the Denver Nuggets.^[16] After scoring 23 points in a 101–94 win over the New Orleans Pelicans, Morris became the third player since 1989 to shoot over 75% from the field in three consecutive games with at least 12 attempts each game; Dwight Howard and Charles Barkley were the first two players to accomplish this.^[17] Morris was named the Western Conference Player of the Week for the November 4-11, 2013 period after averaging 22.8 points, 8.0 rebounds, 2.0 steals and leading the league for field goal percentage (.698).^[18] Morris had 27 points and grab 15 rebounds in a 99–90 victory over the Cleveland Cavaliers, making Morris the first player since Yao Ming in 2002 to score at least 27 points and grab 15 rebounds off the bench.^[19] Because of his improvements throughout the 2013–14 NBA season as a sixth man, Morris ended up being a candidate for both the NBA Most Improved Player Award and the NBA Sixth Man of the Year Award.

2014–15 season

On September 29, 2014, Morris signed a multi-year contract extension with the Suns.^[20] On November 17, 2014, he recorded a then career-high 30 points in the 118–114 victory over the Boston Celtics.^[21] He and Marcus, alongside teammates Goran and Zoran Dragić, all briefly played together for the Suns during the fourth quarter of their 112–96 victory over the Philadelphia 76ers on January 2, 2015. It marked the first time in the NBA's history that two different pairs of brothers played together for the same team at the same time.^[22] On January 13, 2015, Morris scored a career-high 35 points on 15-of-21 shooting in a 107–100 victory over the Cleveland Cavaliers.^[23] In a game against the Dallas Mavericks on March 22, the Morris twins both had double-doubles in the same game for the first time in their careers.^[24]

2015–16 season

On September 8, 2015, Morris was fined $10,000 for conduct detrimental to the league by publicly demanding a trade a month earlier.^[25] He later trained with long-time friend Rasheed Wallace prior to re-joining the Suns for training camp.^[26] On November 23, Morris scored a then season-high 28 points in a loss to the San Antonio Spurs.^[27][28] He started in 16 games to start the season before being benched by coach Jeff Hornacek from December 4 onwards.^[28] During the fourth quarter of the Suns' December 23 game against the Denver Nuggets, Morris threw a towel in the direction of Hornacek as he was heading to the bench.^[29] The following day, Morris was suspended for two games for conduct detrimental to the team,^[30] and was later labelled one of Arizona's biggest sports villains by AZCentral.com.^[31] Following an injury to teammate Alex Len in early January, Morris was reinserted back in the rotation to help fortify the frontcourt.^[32] On February 2, 2016, during Earl Watson's first game as head coach for the Suns, he had a season-best game with 30 points, 11 rebounds, six assists, two blocks, and a steal in a 104–97 loss to the Toronto Raptors.^[33] Four days later, Morris recorded 17 points and a career-high eight assists in a loss to the Utah Jazz.^[34] In his final game with the Suns on February 10 against the Golden State Warriors, Morris and teammate Archie Goodwin got into a physical altercation on the bench and were seen arguing during a timeout. The argument escalated into a shoving match between the pair, as teammates quickly stepped in and separated the two.^[35]

Regular season

Playoffs