Kahn emigrated from Estonia to the United States with his family at age four, becoming a naturalized citizen in 1914. A gifted artist, he forewent a merit scholarship to the Pennsylvania Academy of the Fine Arts to study architecture at the University of Pennsylvania. Trained in a rigorous Beaux-Arts tradition, with a heavy emphasis on drawing, Kahn earned his Bachelor of Architecture in 1924.
After completing his degree, Kahn worked in various firms in Philadelphia, including the offices of Paul Philippe Cret, his former studio critic at the University of Pennsylvania, before forming his own atelier in 1935. His earliest projects included collaborations with both George Howe, an early proponent of the International Style, and the modernist architect Oscar Stonorov and were largely comprised of designs for housing developments in Pennsylvania.