In 2004 Young turned professional. In 2005 he was named the best junior player in the world for a while. In the same year he became the youngest player to win the Australian Open Junior Championships. He then received a lot of attention from the US media celebrating him as the upcoming tennis star. Numerous American organizers gave him a wild card for their ATP tournament . However, he was initially unable to meet the high expectations. At the ATP Masters tournament in Miami in 2006 he lost in the first round against Carlos Berlocq from Argentina with 0: 6 and 0: 6. Berlocq, for his part, then lost his second round match with 0: 6 and 0: 6. Young then concentrated again on smaller tournaments.
He won the Wimbledon Junior Championships in July 2007 against the number 1 in the juniors, Vladimir Ignati .
On August 19, 2007, he won his first ATP Tour singles match when he beat Amer Delić in three sets in New Haven . At the US Open he reached the third round in 2007; there he failed in four sets to Feliciano López .
On October 2, 2011, he reached an ATP final in Bangkok for the first time in his career, which he lost 2: 6 and 0: 6 to Andy Murray .
He is trained by his parents Ilona and Donald Young senior. He is based in Atlanta , Georgia .
In 2018, Young accused fellow countryman Ryan Harrison of racism in his first round defeat in New York . As it later turned out, these allegations were baseless, as the ATP found after an investigation.