In 1904, at age 16, his family moved to a farm in Warrensburg, Missouri. As a youth, he enjoyed speaking in public and joined his school’s debate team. Carnegie said he had to get up at 3 a.m. to feed the pigs and milk his parents’ cows before going to school. During high school, he grew interested in the speeches at the various Chautauqua assemblies. He completed his high school education in 1906.

He attended State Teacher’s College in Warrensburg, graduating in 1908.

After saving $500, Dale Carnegie quit sales in 1911 in order to pursue a lifelong dream of becoming a Chautauqua lecturer. He ended up instead attending the American Academy of Dramatic Arts in New York, but found little success as an actor, though it is written that he played the role of Dr. Hartley in a road show of Polly of the Circus. When the production ended, he returned to New York, living at the YMCA on 125th Street. There he got the idea to teach public speaking, and he persuaded the YMCA manager to allow him to instruct a class in return for 80% of the net proceeds. In his first session, he had run out of material. Improvising, he suggested that students speak about “something that made them angry”, and discovered that the technique made speakers unafraid to address a public audience. From this 1912 debut, the Dale Carnegie Course evolved. Carnegie had tapped into the average American’s desire to have more self-confidence, and by 1914, he was earning $500 (about $12800 today) every week.

By 1916, Dale conducted a lecture at Carnegie Hall. Carnegie’s first collection of his writings was Public Speaking: a Practical Course for Business Men (1926), later entitled Public Speaking and Influencing Men in Business (1932). In 1936, Simon & Schuster published How to Win Friends and Influence People. The book was a bestseller from its debut. By the time of Carnegie’s death, the book had sold five million copies in 31 languages, and there had been 450,000 graduates of his Dale Carnegie Institute. It has been stated in the book that he had critiqued over 150,000 speeches in his participation in the adult education movement of the time.

His first marriage ended in divorce in 1931. On November 5, 1944, he married his former secretary, Dorothy Price Vanderpool (1913–1998), who also had been divorced. Vanderpool had two daughters; Rosemary, from her first marriage, and Donna Dale from her marriage to Carnegie. Dorothy ran the Carnegie company following Dale’s death.

Carnegie died of Hodgkin’s disease on November 1, 1955 at his home in Forest Hills, New York. He was buried in the Belton, Cass County, Missouri, cemetery.