Mario Andrew Pei was born in Rome, Italy, in 1901. Like many Italians of the period, he moved with his family to New York City in 1908. Following his own father's scholarly example, he attended many public and parochial schools. He was an excellent student and was already fluent in five languages by the time he graduated from High School. He went on to learn 30 other languages, as well as the sentence structures of over 100 more languages. His education included receiving a bachelor's degree from City College of New York and a doctorate from Colombia University in 1937.
He started teaching languages at City College in 1923 and joined the Department of Romance Languages at Colombia University in 1928. In 1932, he published "The Italian Language.” During World War II, his language proficiency was put to use as a language consultant to the Office of War Information and the Office of Strategic Services. It was then at he wrote language courses and guides.