He has also played for the Los Angeles Clippers, the Oklahoma City Thunder, the Atlanta Hawks, the Washington Wizards and the Detroit Pistons.

In 2005, Gallinari was acquired by Armani Jeans Milano, which then sent him to Edimes Pavia, a team competing in the Italian league second division championship during the 2005–2006 season, so that he could earn more experience with extended playing minutes.

He posted a season-high 27 points against Maccabi Tel Aviv in his final game,[8] and at the end of the season was named the EuroLeague's Rising Star.

Gallinari's contract with Olimpia Milano had an escape clause for playing professionally in the United States, effectively eliminating major encumbrances that would have prevented him from joining the National Basketball Association (NBA).

On 4 March, Gallinari scored a season-high 17 points against the Atlanta Hawks, shooting 4–5 on three-point field goal attempts.

[13][14] On 31 October 2009, the third game of the 2009 season, Gallinari scored a career-high 30 points and made eight three-pointers in an overtime loss to the Philadelphia 76ers, one short of tying a Knicks franchise record held by Latrell Sprewell and John Starks.

[17] In just his second game with the Nuggets, he almost matched his career high with a 30-point effort in an overtime loss against the Portland Trail Blazers.

[21] On 29 October 2014, Gallinari made his return for the Nuggets, scoring seven points on 1-of-8 shooting in a season opening win over the Detroit Pistons.

[29] On 6 July 2017, the Los Angeles Clippers acquired Gallinari from the Denver Nuggets as part of a three-team trade that sent Jamal Crawford, Diamond Stone and the Clippers' 2018 protected first round draft pick (via Houston) to the Atlanta Hawks and a 2019 second round draft pick from Atlanta (via Washington) to Denver.

[30] In his debut for the Clippers in their season opener on October 19, Gallinari scored 11 points in a 108–92 win over the Los Angeles Lakers.

[31] On 6 December, Gallinari returned to action against the Minnesota Timberwolves after missing a month due to a glute injury.

[42] On 30 June 2022, Gallinari was traded, alongside multiple future first-round picks, to the San Antonio Spurs in exchange for Dejounte Murray and Jock Landale.

On 23 June 2023, the Celtics traded Gallinari to the Washington Wizards as part of a three–team deal involving the Memphis Grizzlies.

[48] On 14 January 2024, Gallinari was traded to the Detroit Pistons, along with Mike Muscala, in exchange for Marvin Bagley III, Isaiah Livers and future draft considerations.

He was later selected for the senior national team to play in EuroBasket 2007, but was forced to withdraw, due to an injury that he suffered in preparation before the tournament.