A small forward, Ariza played college basketball for one season with the UCLA Bruins before being selected in the second round of the 2004 NBA draft by the New York Knicks.

He also played for the Orlando Magic, Houston Rockets, New Orleans Hornets, Washington Wizards, Phoenix Suns, Sacramento Kings, Portland Trail Blazers, and Miami Heat.

Ariza attended Westchester High School in Los Angeles, where as a junior in 2001–02, he combined with teammates and fellow future NBA players Hassan Adams, Brandon Heath, and Bobby Brown to lead the Comets to the California State championship.

[3] He fractured a bone in his right foot in January 2008, but made his return in Game 2 of the Western Conference Finals against the San Antonio Spurs in late May, scoring a basket within his first minute of play.

[11] On October 31, 2009, against the Portland Trail Blazers, Ariza scored a career high 33 points in a 111–107 Rockets win.

On December 13, 2009, Ariza was ejected after he attempted to punch DeMar DeRozan of the Toronto Raptors after having the ball stolen by him.

[12] On April 14, 2010, in the Rockets' final game of the season, Ariza recorded his first career triple-double, tallying 26 points, 10 rebounds, and 10 assists.

On June 20, 2012, Ariza and Emeka Okafor were traded to the Washington Wizards for Rashard Lewis and a draft pick to the New Orleans Hornets.

[14] On February 12, 2014, Ariza recorded a career-high 10 made three-pointers to score a season-high 32 points, as well as 11 rebounds, 3 assists and 3 steals, in a 113–112 loss to the Houston Rockets.

[23] In Game 2 of the 2018 Western Conference Finals, on May 17, 2018, Ariza helped tie the series with 19 points and 6 assists in a 127–105 victory over the Golden State Warriors.

[27][28] In his debut for the Suns in their season opener on October 17, 2018, Ariza recorded 21 points, eight rebounds and seven assists in a 121–100 win over the Dallas Mavericks.

[29] On December 17, 2018, Ariza was traded to the Washington Wizards for Austin Rivers and Kelly Oubre Jr.[30] On January 13, 2019, he narrowly missed his second career triple-double, recording 23 points, 10 assists and nine rebounds in a 140–138 double-overtime loss to the Toronto Raptors.

[35] On November 22, 2020, Ariza, the draft rights to Isaiah Stewart, and a conditional future first-round pick were traded to the Houston Rockets in exchange for Robert Covington.

[36] On November 24, Ariza and Stewart were traded to the Detroit Pistons in exchange for Christian Wood, as part of a sign-and-trade deal.

[39] On March 17, 2021, Ariza was traded to his hometown team the Miami Heat in exchange for center Meyers Leonard and a future second round draft pick.

[49] Ariza's stepfather, Kenny McClary, played at the University of Florida in the mid to late 1980s, and professionally with the Sydney Kings in Australia.