The former U.S. Postal Service rider failed an out-of-competition doping test on Aug. 29, the South African Institute for Drug-Free Sport said, and was provisionally suspended by Cycling South Africa ahead of an independent tribunal. He now faces a two-year ban.
"I fully understand the consequences of my admission and will bear the results of this," George said.
He apologized to his sponsors but Nedbank, the backer of his current 360Life team, said it was immediately withdrawing its sponsorship.
"Nedbank has a zero tolerance towards the use of any banned substances or performance enhancing drugs and does not condone or support such use in any sport," the South African bank said.
George cycled on the disgraced Armstrong's U.S. Postal team in 1999 and 2000 and was one of South Africa's top cyclists having won the South African time trial championships five times and road race championships in 2003.
He said he would not ask for his B sample to be tested and would accept his punishment.
"I know the result will ultimately be the same. This decision will be communicated to Cycling South Africa (CSA) and Drug-Free Sport shortly and according to protocol," George said in his statement.
Armstrong was last month banned for life for doping by the International Cycling Union following a report by the United States Anti-Doping Agency. He was formally stripped of his seven Tour de France titles, wiping out the career of one of cycling's most celebrated riders. Other former teammates of the American testified against him in the report, which said Armstrong used steroids, EPO and blood transfusions.
George won silver in the road race at the 2006 Commonwealth Games in Melbourne and bronze in the time trial in the Kuala Lumpur Games in 1998. He also represented South Africa at two Olympics, in 1996 and 2000.
"Cycling, as you know, has been a confusing space, and although it has given me incredible moments it has also given me experiences that no person or young athlete should have to go through," George said.
EPO, or Erythropoietin, artificially increases the red blood cell count and increases an athlete's oxygen carrying capacity.
"His biological passport indicated suspicious activity and that triggered a targeted test for EPO," SAIDS chief executive Khalid Galant said earlier Tuesday, announcing the positive test. "A subsequent urine test came back positive for the banned EPO drug."
Despite the sport's battered international image, William Newman, the president of Cycling South Africa, said doping was "not endemic" in South African cycling.