He has also played for the Denver Nuggets and New York Knicks, as well as for the Zhejiang Golden Bulls of the Chinese Basketball Association (CBA).

However, after winning co-MVP with Dwight Howard at the 2004 McDonald's All-American Game,[4][6] Smith decided to forgo college and declared for the 2004 NBA draft.

[5] During the 2008–09 season, he averaged 15.2 points over 81 games (18 starts), finishing second in voting for the NBA Sixth Man of the Year Award behind Jason Terry.

[5] On April 13, 2009, Smith had a career-high 45 points and franchise-best 11 3-pointers to help the Nuggets clinch the Northwest Division title and home-court edge in the playoffs for the first time in 21 years with a 118–98 win over the Sacramento Kings.

[12] On December 23, 2009, Smith scored a season-high 41 points against the Atlanta Hawks, becoming the first NBA player ever to record multiple games of 10+ 3-pointers.

A fan favorite in Denver for his 3-point shooting and electric dunks, Smith often drew the ire of coach George Karl for his befuddling shot selection.

[14] In September 2011, due to the NBA lockout, Smith signed a one-year deal with the Zhejiang Golden Bulls of the Chinese Basketball Association (CBA).

[14] In accordance with CBA rules, Smith's contract with the Golden Bulls did not include an opt-out clause that would allow him to return to the NBA following the conclusion of the lockout.

He was subsequently named the NBA Sixth Man of the Year, becoming just the third player in franchise history to win the award, joining Anthony Mason and John Starks.

[23][24] Two days later, in a 102–91 loss to the Miami Heat, Smith broke an NBA record of 21 three-pointers taken in a single game, a mark set in 2005 by Damon Stoudamire.

Smith hit 10 of 22 3-point shots against the Heat, setting a franchise record for 3-pointers made and finishing with 32 points for the second straight game.

[25][26] On January 5, 2015, Smith was acquired by the Cleveland Cavaliers in a three-team trade that involved the Knicks and the Oklahoma City Thunder.

[31] After a contract stalemate that had consumed nearly the first three weeks of training camp, Smith and the Cavaliers reached an agreement on a four-year deal worth $57 million.

[32] On November 1, in a win over the Houston Rockets, Smith hit his 344th three-pointer, passing Damon Jones for ninth place on the team's all-time list.

[33] On November 18, he hit three 3-pointers against the Detroit Pistons to move past Dirk Nowitzki into 15th place on the NBA's career list for 3-pointers.

[34] On December 13, Smith, having been in a season-long shooting slump, scored 17 of his season-high 23 points in the first half of the Cavaliers' 103–86 win over the Memphis Grizzlies.

[40] He found his form on November 7, scoring a season-high 20 points on 5-of-7 3-pointers in a 124–119 win over the Milwaukee Bucks, passing Rashard Lewis (1,787) for 14th place on the NBA's career 3-pointers made list.

[40] On December 14, in a 121–112 win over the Los Angeles Lakers, Smith passed Chauncey Billups (1,830) for 11th place on the NBA's career 3-pointers made list.

Smith, apparently confused and thinking the Cavaliers were leading, attempted to dribble out the clock before realizing his error and frantically passing to George Hill with 1.2 seconds left, in front of a visibly irate LeBron James.

Head coach Tyronn Lue had been fired after an 0–6 start, the team was suffering injuries to All-Star Kevin Love and others, and Smith's role had been reduced.

A day earlier, he had accused the team of not trying to win, saying their goal was to "develop [young players] and lose to get lottery picks.

[49] On July 1, 2020, Smith signed with the Los Angeles Lakers for the remainder of the 2019–20 season, reuniting him with former Cavaliers teammate LeBron James.

[55] On August 11, 2021, it was reported that Smith enrolled at North Carolina A&T State University, aiming for a degree in liberal studies and planning to join the Aggies golf team.

"[63] In June 2016, a Cleveland clothing company began selling a T-shirt which reproduced Smith's torso and upper arm tattoos.

[79] In October 2008, a grand jury in Monmouth County, New Jersey, declined to indict Smith on a vehicular manslaughter charge stemming from the accident.

[80] On August 5, 2009, Smith closed his Twitter account because he was accused of writing in a way that reflected the Bloods gang, specifically replacing his c's with k's.

[81] On August 28, 2009, Smith was suspended seven games for the 2009–10 NBA season in response to his guilty plea to a reckless driving charge related to the fatal 2007 accident.

[85] In May 2012, Smith was arrested in Miami Beach, Florida for failing to appear in court in 2011 after he was cited for operating a motor scooter with no valid license.

[89] In September 2018, the NBA threatened to fine Smith if he appeared in a game without covering up the Supreme logo tattooed on his leg.

Smith initially resisted but, after talking with National Basketball Players Association officials, eventually agreed to hide the tattoo.