Toronto Raptors (2012–2013) On June 29, 2012, Acy was selected by the
Toronto Raptors with the 37th overall pick in the
2012 NBA draft. On July 16, 2012, he signed a multi-year contract with the Raptors. He played sparingly for Toronto in 2012–13 and earned two assignments to the
NBA Development League, where he played for the
Bakersfield Jam. On April 6, 2013, Acy scored a season-high 13 points in the Raptors' 100–83 loss to the
Milwaukee Bucks.
Sacramento Kings (2013–2014) On December 9, 2013, Acy was traded, along
Rudy Gay and
Aaron Gray, to the
Sacramento Kings in exchange for
Greivis Vásquez,
Patrick Patterson,
John Salmons and
Chuck Hayes. Six days later, he made his debut for the Kings in a 106–91 win over the
Houston Rockets, recording four points, three rebounds and one block in 13 minutes off the bench.
New York Knicks (2014–2015) On August 6, 2014, Acy was traded, along with
Travis Outlaw, to the
New York Knicks in exchange for
Wayne Ellington and
Jeremy Tyler. He made his debut for the Knicks in their season opener on October 29, 2014, recording six points, six rebounds, one assist and one block in 21 minutes off the bench in a 104–80 loss to the
Chicago Bulls. On January 5, 2015, he recorded career highs of 19 points and 14 rebounds in a 105–83 loss to the
Memphis Grizzlies. He had a career-best season in 2014–15, averaging career highs in points (5.9), rebounds (4.4), assists (1.0), minutes (18.9) and games played (68).
Return to Sacramento (2015–2016) On July 22, 2015, Acy signed with the Sacramento Kings, returning to the franchise for a second stint. On January 7, 2016, he scored a season-high 18 points in a 118–115 win over the
Los Angeles Lakers.
Dallas Mavericks (2016) On July 20, 2016, Acy signed with his home team, the
Dallas Mavericks. On November 18, 2016, he was waived by the Mavericks after appearing in six games.
Texas Legends (2016–2017) On November 28, 2016, Acy was acquired by the
Los Angeles D-Fenders of the
NBA Development League and then immediately traded to the
Texas Legends, the Mavericks' D-League affiliate. On December 1, 2016, he made his debut for the Legends in a 121–106 win over the
Greensboro Swarm, recording 16 points, seven rebounds and two blocks in 17 minutes as a starter. In 12 games for the Legends, he averaged 17.3 points, 8.1 rebounds, 1.2 assists, 1.6 steals and 2.1 blocks in 31.9 minutes.
Brooklyn Nets (2017–2018) On January 10, 2017, Acy signed a 10-day contract with the
Brooklyn Nets. and a multi-year contract on January 30. On March 3, 2017, he scored a season-high 18 points in a 112–97 loss to the
Utah Jazz. On April 7, 2018, Acy had career highs with six 3-pointers and 21 points in a 124–96 win over the
Chicago Bulls.
Phoenix Suns (2019) On January 7, 2019, Acy signed a 10-day contract with the
Phoenix Suns. On January 17, he signed a second 10-day contract with the Suns. On January 25, Acy recorded a season-high 10 rebounds in a blowout loss to the
Denver Nuggets. Two days later, Quincy left the
Phoenix Suns after his second 10-day contract expired.
Return to Texas (2019) On February 24, 2019, the
Texas Legends announced that Acy had returned to their team.
Shenzhen Leopards (2019) On March 15, 2019, Acy agreed to a deal with the
Shenzhen Leopards. On March 24, 2019, Acy was registered for the season, replacing
Dwight Buycks. On March 26, 2019, after appearing in one game for Shenzhen, Acy was, in turn, replaced by Buycks.
Maccabi Tel Aviv (2019–2020) On July 31, 2019, Acy signed with
Maccabi Tel Aviv of the
Israeli Premier League and the
EuroLeague, signing a one-year deal with an option for another one. On November 16, 2019, Acy recorded a new career-high 22 points, shooting 9-of-12 from the field, along with six rebounds and six dunks in a 94–57 win over
Maccabi Ashdod.
Olympiacos (2021–2022) On November 3, 2021, Acy signed with
Olympiacos of the
Greek Basket League and the
EuroLeague. In four EuroLeague games, he averaged 4.3 points, 3.1 rebounds, 4.4 PIR and 0.7 blocks in 10 minutes per game. He was let go by Olympiacos in mid-July 2022. ==Coaching career==