Knotts was born in Morgantown, West Virginia. His ambition from an early age was getting into show business, which since his school years was the only business he's ever known. As a child he was a movie aficionado and radio fan, with a particular love for comedy. From age twelve, Knotts was constantly trying to copy the impeccable timing of his idol, Jack Benny. Another radio favorite, The Edgar Bergen Show, inspired Knotts to learn ventriloquism, and throughout high school he entertained civic groups with an act he admits he borrowed directly from Bergen.

After high school, Knotts enrolled as a speech major at West Virginia University, intending to teach. However, the army called, and he spent the next few years touring the South Pacific doing comedy routines in Stars and Gripes. Thus bitten, it was only natural that he would eventually finish his degree and head for New York City and show business.

In the years that followed, Knotts appeared on various radio and television programs until he landed his Broadway debut in No Time for Sergeants. During the show's hit run, the actor began to develop what would become his signature character of the nervous little man, now familiar to audiences everywhere, which he based on an after-dinner speaker he had seen back home in Morgantown.

Knotts became a featured performer on The Garry Moore Show and The Steve Allen Show, and when Allen's show moved to Hollywood, Knotts followed. He was in the right place at the right time to be picked to join Andy Griffith in the legendary series that made him a household name. In the decades after The Andy Griffith Show finished its run, Knotts continued to win recurring roles on series television, most memorably as Ralph Furley in Three's Company.

Knotts' movie credits include The Incredible Mr. Limpet, The Ghost and Mr. Chicken, The Reluctant Astronaut, The Shakiest Gun in the West, It's a Mad Mad Mad Mad World and The Prize Fighter. The Disney animated feature, Chicken Little, marked a homecoming of sorts for this former member of Disney Studios' 1970s-era stable of feature players, star of so many of the studio's family matinee offerings including The Apple Dumpling Gang, No Deposit, No Return, Gus, Herbie Goes to Monte Carlo, Hot Lead and Cold Feet and The Apple Dumpling Gang Rides Again.

His theatre credits include Mind with the Dirty Man, Norman Is That You?, Harvey, You Can't Take It With You, Last of the Red Hot Lovers, The Odd Couple, A Good Look at Boney Kern and On Golden Pond.

Knotts passed away February 24, 2006 at Cedars Sinai in Beverly Hills. He was 81.