The agency said the Welsh boxer had been banned for six months after testing positive for methylhexaneamine (MHA) following a fight in March.
Methylhexaneamine, a product which is claimed to promote mental and physical performance and aid weight loss, can be found in several nutritional supplements and is sometimes known as the rather harmless-sounding geranium derivative.
UK Anti-Doping chief executive Andy Parkinson said Maccarinelli's violation was a reminder of the country's tough stance on doping ahead of the Games.
"This is a timely reminder that, no matter what your sport, under the principle of strict liability athletes must exercise extreme caution over what they put into their body," he said.
"With this in mind, Olympic athletes should be aware that they are now in competition from 16 July until 12 August and could be tested at anytime, anywhere.
"MHA is available in a range of supplement products, is banned in competition, and can often be listed under a number of different names," he added.
Maccarinelli once held the WBU and WBO versions of the cruiserweight title but his career suffered a setback when he was stopped by David Haye in London in 2008.
He tested positive for methylhexaneamine after winning the British cruiserweight title against Shane McPhilbin in March.
"I am very conscious of my reputation within the sport of boxing and even prior to the decision that has been released today I promised to fully accept any punishment that was given as a result of this positive test," Maccarinelli, who said he inadvertently ingested the substance after buying a product known as a "fat burner", said in a statement.
Maccarinelli said he had vacated his British title and would assist UKAD in educating other boxers and sportsmen about the dangers of apparently legitimate supplements.
As a professional, Maccarinelli had not been eligible for the Olympics.