Leo Burnett was born on October 21, 1891 in St. Johns, Michigan. His father ran a dry goods store. As a youth, Burnett worked with his father in the store. He grew up watching his father designing ads to promote his business. During his high school, he worked as a reporter for a local, rural newspaper in the summers. Burnett attended the University of Michigan and received his bachelor's degree in 1914. His early dream was to become the publisher of The New York Times and worked as a police reporter for a newspaper in Peoria, Illinois for one year. After realizing the future growth possibilities in advertising, Burnett decided of a career change. In the year 1917, he moved to Detroit, where he got a job in the Cadillac Motor Company as a copywriter and by the end of 1919, he became advertising manager in the company.

During World War I, he joined the navy for six months. After the war ended, he moved his family to Indianapolis, Indiana. He joined a new car company LaFayette Motors, founded by former Cadillac employees as the advertising manager. After working for a while, he was hired by a local advertising agency, the Homer McGee Company. Burnett worked at the agency included handling automobile ads for several accounts. Even though he tried to find jobs in New York for better advertising growth opportunities, he had to remain contented with his position in the company. In 1930, Burnett was hired by Erwin Wasey & Company of Chicago to assume the position of vice-president and the creative head of the company. After working five years, he left Erwin Wasey & Company to form his own agency.

Leo Burnett formed his own company on August 5, 1935 with the name, The Leo Burnett Company. The company was based in Chicago, with an initial capital investment of $50,000 and several employees from Erwin, Wassey, including O'Kieffe. One of the unique features of this company was its establishment in Chicago, as the major players in the advertising were located on Madison Avenue in New York City. The first few years were hard for the company, its initial accounts were, “women’s products” and the clients included The Hoover Company, Minnesota Valley Canning Company, and Realsilk Hosiery Mills. In the first year of its establishment, the company billed less than $1million. But this did not deter Burnett as he worked hard for days and nights, except on Christmas. Those days, ads were primarily focused on words, giving long explanations persuading the consumer to buy the product. Burnett rejected the idea of misguiding the consumers by the use of fashionable devices of contests, premiums, sex and tricks. Instead he advocated the use of product itself, which included the enhancement of good artwork, real information, recipes and humor. Burnett was known for breaking the usual norms and rules. For instance, during the mid 1940s, it was a taboo to show raw meat in advertising, but Burnett while campaigning for the American Meat Institute, showed the raw, red meat in more intense redder background. This unusual approach instantly got consumer’s attention, encouraging Burnett to look for more out-of-the-box ideas.

In the first decade of its establishment, The Leo Burnett Company billed around $10million. With the end of World War II, company’s billings increased, doubling to $ 22 million in 1950. It doubled again in 1954, to make it $55 million. There were many reasons behind company’s manifold increase. One of the critical factors was bringing in major clients like Kellogg, Pillsbury, Procter & Gamble, and Campbell Soup. During 1950s, television became a powerful advertising force and Burnett’s company expanded due to its emphasis on visual presentation. In that decade, Burnett and his company created various advertising icons that stayed for decades. These included, Charlie the Tuna for Starkist Tuna, Tony the Tiger for Kellogg's Frosted Flakes, the underemployed Maytag repairman, and the Jolly Green Giant. His company was known for depicting the American values of strength, tradition, comfort, and family in its advertising campaigns. His famous the Jolly Green Giant was based on folklore, hence was familiar to many consumers. The Jolly Green Giant was created for one of company’s oldest clients, the Minnesota Canning Company. This campaign dramatically propelled the sales of the company so much so that eventually the company renamed itself as Green Giant.

Another very famous and successful advertising icon of the company was the Marlboro Man. Before this ad campaign, filter cigarettes were considered feminine, but after using the manly cowboys in the campaign, these cigarettes became very masculine products. This ad campaign made Marlboro, the best selling cigarettes in the world. By 1959, his company was billing over $100 million annually. Even after the company grew exponentially in terms of clients and billings, Burnett remained actively involved in every project. In 1961, Burnett became the original inductee in the Copywriters Hall of Fame. As the years passed, the company gained recognition for creating original icons and slogans. In 1965, his company created the Pillsbury Doughboy. In 1968, the company created the Keebler Elves and Morris the Cat for 9-Lives cat food. Some of Burnett’s slogans lived for decades, which included the famous slogan, “You're in good hands with Allstate” for Allstate Insurance Company. When his company was hired by the United Airlines in mid 1960s, the company came up with the famous slogan, “Fly the Friendly Skies of United”, which was used in variations for over three decades.

Leo Burnett died of a heart attack on June 7, 1971 at his home in Lake Zurich, Illinois.