A graduate of Lafayette High, Livingston made the announcement after Stage 18 on Friday in Bourg-en-Bresse, France, saying he wanted to spend more time with his wife, Becky, and daughter, Kate, born in December.
"Time away from family can never be retrieved, and the monetary rewards of cycling cannot pay back the energy and exuberance of youth," Livingston, 29, said in a statement.
A professional for eight years, Livingston excelled as a climber. He gained notoriety as one of the mountain men for Armstrong when he won the Tour de France in 1999 and 2000. He rode in front of Armstrong on the tough climbs until Armstrong was ready to launch his breakaway to the finish. For the past two years, Livingston has ridden with Team Deutsche Telekom in the same role. He helped Jan Ullrich to a second-place finish last year.
As a member of the U.S. National Team, Livingston won the Junior World Trials in 1991. He then joined the Saturn team and won the U.S. Amateur Championships in 1994. He turned pro the following year as a member of the Motorola team and joined Cofidis in 1997 before signing on with Armstrong and the U.S. Postal Service team in 1999.
In his book "It's Not About the Bike," Armstrong wrote that Livingston was the first of his cycling friends to learn that Armstrong had been diagnosed with testicular cancer.
Livingston will finish his sixth Tour de France on Sunday. His highest finish was 17th of 189 riders, in 1998. After Friday's stage, he was 57th overall.
"Rather than being burned out, I am on fire with an exuberance for living, which has been stoked for the last 15 years by my cycling life," Livingston said in the statement. "My prayer is that my contribution to this sport is one that will be emulated by those who follow and that the sport of cycling will continue to flourish."
Livingston's father, John, said Kevin probably would return to the U.S. after the cycling season and perhaps pursue a law degree.