The American was fired by Omega Pharma in October following his admission during an investigation by the United States Anti-Doping Agency into shamed compatriot Lance Armstrong.
"I'm retired," he told The Press Democrat on Sunday on the sidelines of the final stage of the Amgen Tour of California.
"It's just been an unceremoniously retired," Leipheimer said. "I sort of miss racing. I still love riding my bike."
The 39-year-old veteran -- who rode with Armstrong for US Postal in 2000 and 2001 and then again with Discovery Channel in 2007 -- served a six month suspension imposed by USADA that ended March 1.
Leipheimer admitted to taking several banned substances including EPO and testosterone, as well as using blood transfusions, which are prohibited.
His results between June 1, 1999, to July 30, 2006 and July 7 to July 29, 2007 - the periods of time he admitted to doping as he continued with other teams such as Rabobank and Gerolsteiner - were erased from the record.