Dunston was born in southern Kentucky, and grew up in LeFrak City, Queens. He is a graduate of St. John's Preparatory High School. He is the nephew of former professional baseball player Shawon Dunston, a former No. 1 pick in the MLB.
Dunston attended Fordham University, where he played college basketball with the Fordham Rams. He finished his collegiate career by being named to the First Team All-Metropolitan, Second Team All-Atlantic 10 Conference, and Atlantic 10 Conference All-Defensive Team.
In his college career, Dunston appeared in all 120 of Fordham's games, starting in 118 of them. He finished his college career in second place on Fordham's all-time scoring list, with 1,832 career points, in third place on Fordham's all-time rebounds list, with 993 career rebounds, and as Fordham's career blocked shots leader, graduating with 294 career rejections.
Dunston played with Mobis Phoebus in the Korean Basketball League. In 2010, he signed with the Greek League club Aris, but left the team in February 2011. After leaving Aris, he signed with the Israeli League club Bnei HaSharon. Following the 2010-11 season, Dunston joined the Israeli League club Hapoel Holon.
Reports said that Dunston was on the verge of signing a guaranteed contract with the NBA's Brooklyn Nets in the summer 2012. However, he joined the Italian League club Pallacanestro Varese instead.
On July 9, 2013, Dunston signed a two-year contract with Olympiacos. In his first EuroLeague season, he averaged 10.3 points, 5.3 rebounds, 1.1 steals and league-leading 1.3 blocks over 29 games played. Olympiacos however finished the participation in the EuroLeague by losing 2–3 to Real Madrid in the quarter-final series. On May 6, he was voted the EuroLeague Best Defender of the season.
On May 6, 2015, he was named the EuroLeague season's Best Defender for the second season in a row.
On June 23, 2015, Dunston signed a two-year contract with the Turkish club Anadolu Efes. On May 18, 2017, he signed a two-year contract extension with Anadolu Efes.
On June 16, 2015, he was included on the list of candidates of the senior Slovenian national basketball team for the EuroBasket 2015, by team selector Jure Zdovc. However, he didn't get a Slovenian passport in time, so he wouldn't represent Slovenia at the EuroBasket.
In June 2016, Dunston arrived in Yerevan, to represent the senior Armenian national basketball team in the 2016 FIBA European Championship for Small Countries.
Note: The EuroLeague is not the only competition in which the player participated for the team during the season. He also played in domestic competition, and regional competition if applicable.Atlantic 10 Conference Rookie of the Year: (2005)
Second Team All-Atlantic 10 Conference: (2005)
First Team All-Atlantic 10 Conference: (2006)
Second Team All-Atlantic 10 Conference: (2007)
First Team All-Metropolitan: (2008)
Second Team All-Atlantic 10 Conference: (2008)
Atlantic 10 Conference All Defensive Team: (2008)
Israeli Super League Quintet: (2012)
FIBA Intercontinental Cup Champion: (2013)
2× EuroLeague Best Defender: (2014, 2015)
Greek League Champion: (2015)
Greek League Best Defender: (2015)
Turkish President's Cup: Winner (2015)
BSL All-Star: (2017)
All-EuroLeague Second Team (2017)