Leo Burnett was born in St. Johns, Michigan. He studied journalism at the University of Michigan and then worked as a police reporter for the Peoria Journal. Subsequently, in 1919 Burnett worked in the ad department of the Cadillac Motor Company and became the advertising manager. After this, Burnett joined Lafayette Motors, then to the Homer McKee Agency in Indianapolis and finally the Erwin, Wasey and Company.

A number of years later, in 1935, Burnett borrowed $50,000 to establish is own company. It became the Leo Burnett Company, Inc. A friend of Burnett’s named Jack O’Kieffe partnered with Burnett at the beginning. Starting with three clients who included Green Giant, Hoover, and Realsilk Hosiery, the fledgling managed just under a million dollars in revenue.

Leo Burnett’s advertising company struggled tremendously in its first year of operation, failing to bring in such significant prospects as the Hershey Chocolate Company and Wrigley’s Gum. With time and a little effort, company started to gain strength. By 1940 Burnett obtained an account with the American Meat Institute. Five years later, he launched what would become a very memorable campaign, in which red meat was placed on a red background and the copy urged the reader to eat more meat. It was the first of many examples of Burnett’s technique of “stressing the inherent drama in the product.”

It wasn’t until 1949 that Burnett’s company saw it most dramatic period of growth. With the acquirement of Pillsbury Family Flour account, Burnett created the well-known Pillsbury Bake Off.  This became a dramatic attention-getting campaign. After this, Burnett acquired the Kellogg’s Cereal advertising account. The combination of both accounts made the Burnett Company’s notoriety skyrocket.

Burnett earned the account of the New York based Tea Council. This account signaled to the New York based advertising giants that a new advertising agency in Chicago was emerging. In 1950, Proctor and Gamble contracted with the Burnett Company Inc. for an institutional campaign, sealing the Burnett Company's level of importance in the advertising industry. Burnett was also responsible for the transformation of Marlboro cigarettes’ image from an unknown cigarette brand to a highly successful name in the industry. In subsequent years, Burnett continued to acquire other major accounts including Schlitz Beer, Allstate, Maytag and United Airlines.

Leo Burnett's agency was a model of the socially responsible big business. There were two dimensions to this professional performance: one, participation in civic affairs like involvement in benevolent organizations and charities; and two, a strong and responsible work ethic that stressed fair dealing.