Clemens was born in Dayton, Ohio, the fifth child of Bill and Bess (Lee) Clemens. He is of German descent, his great-grandfather Joseph Clemens having immigrated in the 1880s. Clemens's parents separated when he was an infant. His mother soon married Woody Booher, whom Clemens considers his father.

Clemens has appeared as himself in several movies and television episodes and has also occasionally acted in films. Perhaps best known was his appearance in the season three episode of The Simpsons ("Homer at the Bat") where he is hypnotized into thinking he is a chicken (he did his own clucking). Clemens has also made guest appearances as himself on the TV shows Hope & Faith, Spin City, Arli$$, and Saturday Night Live as well as the movie Anger Management, and makes a brief appearance in the movie Kingpin as the character Skidmark. He also is shown playing an actual game with the Houston Astros in the film Boyhood.  He appeared in the 1994 movie Cobb as an unidentified pitcher for the Philadelphia A's. In 2003, he was part of an advertising campaign for Armour hot dogs with MLB players Ken Griffey Jr., Derek Jeter, and Sammy Sosa. Since 2005, Clemens has also appeared in many commercials for Texas-based supermarket chain H-E-B. In 2007, he appeared on a baseball-themed episode of MythBusters ("Baseball Myths"). He has also starred in a commercial for Cingular parodying his return from retirement. He was calling his wife, Debra Godfrey, and a dropped call resulted in his return to the Yankees.  He released an early autobiography, Rocket Man: The Roger Clemens Story written with Peter Gammons, in 1987. Clemens is also the spokesperson for Champion car dealerships in South Texas. In April 2009, Clemens was the subject of an unauthorized biography by Jeff Pearlman, titled The Rocket that Fell to Earth-Roger Clemens and the Rage for Baseball Immortality, that focused on his childhood and early career and accused Mike Piazza of using steroids. On May 12, Clemens broke a long silence to denounce a heavily researched expose by four investigative reporters from the New York Daily News, called American Icon: The Fall of Roger Clemens and the Rise of Steroids in America's Pastime. Clemens went on ESPN's Mike and Mike show to call the book "garbage", but a review by Michiko Kakutani of The New York Times called the book "gripping" and compared it to the work of Bob Woodward.

how did clemens reacT?
Clemens went on ESPN's Mike and Mike show to call the book "garbage",