Purchase, a forward who played for the Australian Under 17 National Team, is considered a strong offensive player with good outside shooting skills.
"I am so excited about my decision and I can't wait to get started," Purchase told Inside the Auburn Tigers "I am looking forward to the challenge."
Purchase plays for one of the top club teams in Australia, the Melbourne Tigers. He is expected to sign with the Tigers in the early period in November along with six-foot-six forward Sam Logwood from La Lumiere School in La Porte, Ind.
Last season he averaged 21.3 points, 8.7 rebounds and 5.8 assists for the Melbourne Tigers and hit 47.8 percent of his three-pointers.
Logwood and Purchase both took official visits to Auburn last weekend.
Coach Tony Barbee's Tigers, who are expected to sign three players for their 2014 class, are scheduled to have 6-5, 190 guard/forward Milik Yarbrough on campus this weekend for an official visit. Yarbrough attends Zion-Benton Township High in Illinois.
Purchase took his official visit to Auburn along with his father, Jack Purchase, who was a standout performer on the Australian basketball scene.
The Tigers have three freshman international players on the 2013-14 roster with Benas Griciunas from Lithuania, Dion Wade from Belgium and Matthew Atewe from Canada. While the women's team has had players from Australia, Purchase would be the first player from that country for an AU men's basketball squad.
The women's basketball team also picked a pair of commitments this week when twins Jazmine and Jessica Jones of West Forsyth High in North Carolina pledged to sigh with Coach Terri Williams-Flournoy's Tigers after taking an official visit to Auburn over the weekend.
Jazmine, a 6-2 forward, averaged 15 points and six rebounds per game as a junior. Jessica, a 6-0 small forward, averaged 11 points and nine rebounds last season.