[10] After an injury to Patrick Patterson, Rockets head coach Kevin McHale named Morris the opening day starter at power forward for the 2012–13 season.

When told he would be starting, Morris thought McHale was kidding, since he rarely played his rookie season and was hurt during the preseason.

[16] On January 7 game against the Minnesota Timberwolves, Morris received a technical foul and was caught on national TV berating head coach Jeff Hornacek about the situation.

[22] On July 9, 2015, Morris was traded to the Detroit Pistons, along with Reggie Bullock and Danny Granger, in exchange for a 2020 second-round draft pick.

[25] The Pistons finished the regular season as the eighth seed in the Eastern Conference with a 44–38 record, earning a playoff berth for the first time since 2009.

[27] On July 7, 2017, Morris was traded to the Boston Celtics in exchange for Avery Bradley and a 2019 second-round draft pick.

[30] On January 5, 2020, Morris scored a career-high 38 points and tied his career high for field goals made (13) in a 135–132 loss against the Los Angeles Clippers.

In the first round of the 2020 NBA playoffs, he was ejected during Game 6 after committing a flagrant foul on Luka Dončić and was fined $35,000, but was never suspended.

[33] In the 2020 Western Conference Semifinals, Morris notably had an altercation with Paul Millsap as the Clippers fell in seven games after the Nuggets came back from a 3–1 series deficit.

[34] On November 1, 2023, the Philadelphia 76ers acquired Morris, Nicolas Batum, Kenyon Martin Jr. and Robert Covington from the Clippers in exchange for James Harden, P. J. Tucker, and Filip Petrušev.

[35] On February 8, 2024, Morris was traded to the San Antonio Spurs in a three-team deal involving the Indiana Pacers.

[48] The Morris brothers and former teammates Goran and Zoran Dragić all briefly played for the Suns during the fourth quarter of the team's January 2, 2015 112–96 victory over the Philadelphia 76ers.

The case against the Morris brothers was first brought on August 3, 2015;[53] the trial concluded on October 3, 2017, with the twins and Gerald Bowman found not guilty and the accused Julius Kane and Christopher Melendez Jr. confessing their guilt in September 2017.

In spite of the resolution the incident was considered a catalyst for the Suns trading Marcus to the Pistons on July 9, 2015[54] and a factor in dealing his brother to the Washington Wizards on February 18, 2016.

The Morris twins helped create the Family Over Everything Foundation, an organization that assists members of under-served communities in Philadelphia and other cities.