While running for Overfelt High School in San Jose, California, Evans was undefeated in his high school career, improving his 440-yard time from 48.2 in 1964 to 46.9 in 1965. He attended San Jose State, where he was coached by Hall of Famer Lloyd (Bud) Winter. As a freshman, he won his first AAU championship in 440 yd (402.34 m) in 1966. He won the AAU title four years in a row (1966–1969) and again in 1972 and added the NCAA 400 m title in 1968. His only defeat during that streak came at the hands of San Jose State teammate Tommie Smith. The two were so competitive, Winter could not let them practice together.
Lee Evans achieved his first world record in 1966, as a member of the USA national team which broke the 4 x 400 m relay record at Los Angeles, the first team to better 3 minutes (2:59.6) for the event. The next year he broke the 4 x 220 yd (201.17 m) relay world record at Fresno in a time of 1:22.1.
In 1967, Evans won the 400 metres at the Pan American Games, in an automatic time of 44.95, which (in the era of hand times) was the first bona fide automatic time to break 45 seconds.
Evans won the 1968 Olympic trials at Echo Summit, California with a world record 44.06 and demolished it in the Olympic final, winning in 43.86, from which he still stands as the tenth best performer in history. Evans won a second gold as the anchorman on the 4 x 400 m relay team, setting another world record of 2:56.16. Both the times stood as a world record for almost twenty years (the relay, for almost 24 years). While accepting the relay Gold medal Evans, with fellow African-American medalists Larry James and Ron Freeman, received their medals wearing berets in imitation of the Black Panther Party.
After winning the AAU 400 m titles in 1969 and 1972, Evans finished only fourth in the 1972 Olympic trials, but was named a member of the 4 x 400 m relay team once more. However, the United States couldn't field a team because Vincent Matthews and Wayne Collett were suspended for a demonstration at a medal ceremony similar to the one staged by Tommie Smith and John Carlos in the previous Olympics. Evans became a professional after the 1972 season joining the International Track Association (ITA) tour. He had some success on the ITA tour notably setting a 600 m indoors world best at the first meet in Idaho State University'sMinidome. The ITA folded in 1976 and Evans was reinstated as an amateur in 1980 and ran a 46.5 in one of his few appearances that year, at the age of thirty-three. Evans went on to head the national athletics programs in six different African Nations before accepting a position as head cross country/track & field coach at the University of South Alabama.
Upon fulfilling his contract, Evans plans to return to either Africa or Mexico where "you are truly free – not like this fake freedom America has everybody believing in."