The 39-year-old German, who was banned for two years in 2012 for a doping offence, had previously confessed to having contact with Eufemiano Fuentes but consistently denied being illegally assisted by the doctor.
On Saturday, however, Ullrich was quoted in German weekly news magazine Focus as saying he had been helped by Fuentes.
"Yes I did undergo Fuentes's treatments," the 1997 Tour de France champion said. "Almost everyone took performance-enhancing substances back then.
"I did not take anything that the others did not take. Cheating starts for me when I gain an advantage. That was not the case. I wanted to have equal chances."
Ullrich, who was among his country's most popular athletes before his doping past unravelled, said he had he used his own blood for the treatment and that he was "no better or worse" than Lance Armstrong.
"I always knew Lance Armstrong would not get away with it, even if he was probably for years protected by one or the other institutions and the world governing body," he said.
"Neither of us thought we were guilty of anything. I'm not better than Armstrong but no worse. The great heroes of the past are today people with flaws with which we must cope. "
"This is too little, too late," German Olympic Sports Confederation president Thomas Bach told reporters. "Jan Ullrich had his chance for a creditable admission a couple of years ago and he missed it.
"Today's confirmation of some of the already well-known and established facts does not help Jan Ullrich nor cycling," Bach, a candidate for the International Olympic Committee presidency, said.
Fuentes, at the centre of a much-publicised trial in Spain earlier this year, told the court that as well as cyclists, his clients included football players, athletes, tennis players and boxers.
The Operation Puerto scandal broke in 2006, when Spanish police launched raids that uncovered more than 200 code-named blood bags, some of which were linked to cyclists.
Ullrich, who retired in 2007 after also winning gold and silver medals at the Sydney 2000 Olympics, remains the only German to win the Tour de France.
In February 2012, Ullrich was found guilty of a doping offence by the Court of Arbitration for Sport and retroactively banned for two years from August 22, 2011.
In addition to the ban, all results after May 2005 were removed from his list of achievements.
- Sports & Recreation
- Jan Ullrich
- Eufemiano Fuentes
- Lance Armstrong