Mandino was once the editor of his high school paper and planned to attend the University of Missouri's journalism school.
Mandino gained prominence as the insurance salesperson turned motivational writer and speaker whose book The Greatest Salesman in the World met with huge success. After serving in the U.S. Army Air Corps during World War II, and receiving the Distinguished Flying Cross for his missions as a navigator, Mandino returned to a series of odd jobs before landing a position in 1948 with the Metropolitan Life Insurance Company in Boston. In 1960, he left Met Life for Combined Insurance Company in Chicago, and in 1965 he became the executive editor of Success Unlimited, a motivational and inspirational magazine. In 1968, The Greatest Salesman in the World was published. The book was based on a short story he wrote for Success Unlimited, about a young boy who gives his blanket to the baby Jesus. His other works include A Better Way to Live, The Greatest Miracle in the World, The Christ Commission, Secrets for Success and Happiness, and Og Mandino's University of Success.
Mandino's main philosophical message is that every person on earth is a miracle and should choose to direct their life with confidence and congruent to the laws that govern abundance. He claimed that all successful people take on their own lives by "charting" or consciously choosing both the desired destination and the path to reach it.
Served to First lieutenant United States Army Air Force, 1942-1945. Member Authors Guild, Authors League, National Speakers Association, International Speakers Hall of Fame.
Married Bette L. Lang, December 9, 1957. Children: Dana, Matthew.