His father, Clark Hayes, operated the Hayes Hotel in Stannards and was also involved in oil production. George Hayes grew up in Stannards and attended Stannards School. He played semiprofessional baseball while in high school. He ran away from home in 1902, at 17, joined a stock company, apparently traveled for a time with a circus, and became a successful vaudevillian.

Hayes married Olive E. Ireland, the daughter of a New Jersey glass finisher, on March 4, 1914. She joined him in vaudeville, performing under the name Dorothy Earle (not to be confused with film actress and writer Dorothy Earle). Hayes had become so successful that by 1928, at age 43, he was able to retire to a home on Long Island in Baldwin, New York. He lost all his savings the next year in the 1929 stock-market crash. Olive persuaded her husband to try his luck in films, and the couple moved to Los Angeles. They remained together until her death on July 5, 1957. The couple had no children.

His siblings included his brothers, William W. Hayes, Morrison Hayes, Clark B. Hayes, and his sisters, Nellie Elizabeth Hayes Ebeling and Harriet “Hattie” Elizabeth Hayes Allen. His brother, Morrison Hayes, a Corporal in the United States Army, was killed in action on July 19, 1918, during World War I in France and was awarded the Distinguished Service Cross for his actions during the war.

From 1935 to 1939, Hayes played the part of Windy Halliday, the humorous “codger” sidekick of Hopalong Cassidy (played by William Boyd). In 1939, Hayes left that role at Paramount Pictures, in a dispute over his salary. and moved to Republic Pictures. Since Paramount held the rights to the name Windy Halliday, they renamed him Gabby Whitaker, in virtually the same role. As Gabby, he appeared in more than 40 films between 1939 and 1946, usually with Roy Rogers (44 times), but also with Gene Autry (7) and Wild Bill Elliott (14), often working under the directorship of Joseph Kane (34).

Hayes was also repeatedly cast as a sidekick of the Western stars Randolph Scott (six times) and John Wayne (fifteen times, some as straight or villainous characters). Hayes played Wayne’s sidekick in Raoul Walsh’s Dark Command (1940), which featured Roy Rogers in a supporting role. Hayes became a popular performer and consistently appeared among the 10 favorite actors in polls taken of moviegoers of the period. He appeared in either one or both the Motion Picture Herald and Boxoffice Magazine lists of Top Ten Money-Making Western Stars for twelve straight years and a thirteenth time in 1954, four years after his last film.

The Western film genre declined in the late 1940s, and Hayes made his last film appearance in The Cariboo Trail (1950). He moved to television and hosted The Gabby Hayes Show, a Western series, from 1950 to 1954 on NBC and, in a new version in 1956, on ABC. The show was sponsored by Quaker Oats, whose products were prominently advertised during the show. Gabby would promote the puffed wheat product by saying to stand back from the screen and firing a cannon loaded with cereal at the screen as a tie in to their ad slogan ‘shot from a guns’. He introduced the show, often while whittling on a piece of wood, and would sometimes throw in a tall tale. Halfway through the show, he would say something else, and at the end of the show, also, but he did not appear as an active character in the stories. When the series ended, Hayes retired from show business. He lent his name to a comic book series, “Gabby Hayes Western” comics, published by Fawcett Publications from November 1948 until January 1957, and to a children’s summer camp in New York.

Following his wife’s death on July 5, 1957, Hayes lived in and managed a 10-unit apartment building he owned in North Hollywood, California. At the beginning of 1969, he entered Saint Joseph Hospital in Burbank, California, for treatment of cardiovascular disease. He died there on February 9, 1969, at the age of 83. He is interred in the Forest Lawn–Hollywood Hills Cemetery in Los Angeles.

Since April, 1969, a band of fishermen has traveled to Kettle Creek, Potter County, Pennsylvania, for the “Gabby Hayes Memorial Trout Fishing Tournament”. These men, known as Gabby Guys, gather annually to celebrate the opening day of the trout fishing season and the memory of Hayes. In April 2019, they celebrated their fifty year anniversary, which also marked 50 years since Hayes’ passing.

Homage was paid to Hayes in a different way in the 1974 satirical Western Blazing Saddles. The actor and director Jack Starrett, credited as Claude Ennis Starrett, Jr., played a Hayes-like character. In keeping with a running joke in the movie, the character is called Gabby Johnson. After Johnson delivers a rousing, though partially unintelligible speech to the townspeople, David Huddleston’s character stands up to say, “Now, who can argue with that?!”, and proclaims it “authentic frontier gibberish.”

Two stars on the Hollywood Walk of Fame commemorate Hayes’s work in the entertainment industry: one for his contribution to radio, at 6427 Hollywood Boulevard, and one for his contribution to television, at 1724 Vine Street. In 2000, he was posthumously inducted into the Western Performers Hall of Fame at the National Cowboy and Western Heritage Museum in Oklahoma City, Oklahoma.