With a career spanning more than fifty years, John Caples is considered one of the advertising industry’s most effective copywriters. His career in copywriting began at Ruthrauff & Ryan gaining solid experience creating results-oriented mail-order copy. It was there that he wrote, arguably, one of the 20th century's most successful results-oriented ads. Written for the U.S. School of Music, the ad: "They laughed when I sat down at the piano—but when I started to play!” illustrated very effectively Caples’ idea that most people want to be carefree and popular. Caples preferred simplicity and straight talking whether teaching, lecturing or writing.

In 1927, Caples started working for Batten, Barton, Durstine & Osborn and continued there for another fifty-six years. By 1941 Caples was the company’s vice president. In later years, he became the creative director. The only lapse in working career was when he, like so many Americans, entered World War II. He served as a naval commander.

Caples received awards and recognitions for his professional contributions including a place in the Copywriters Hall of Fame as well as the Advertising Hall of Fame, 1973 and 1977 respectively.

John Caples also wrote several books throughout his career including Tested Advertising Methods (1932), Advertising Ideas (1938) and Making Ads Pay (1957). Each work was a testament to his long-held views on advertising. Caples believed in testing of ads, consistency in copywriting practice, and simplicity in advertisements. Unlike many ad copyists, Caples made no secret of his dislike of humor being used in ads. What he said on one occasion is illustrative: “Only half of the people in this country have a sense of humor, and clever ads seldom sell anything."

The John Caples International Awards were founded in his honor by Andi Emerson in 1977. Caples died on June 10, 1990, at the age of ninety.