Born in country Victoria, La Fontaine lived in Footscray during his early years. He attended St. Joseph's CBC North Melbourne (later St. Joseph's College Melbourne) from 1925 to 1929 where he earned the title Captain of College for 1927, 1928 and 1929. La Fontaine went on to complete his secondary education at St Kevin's College, Melbourne before proceeding to university where he eventually gained a Bachelor of Science.
During the second world war, La Fontaine served as a Flying Officer with the RAAF between 1942 and 1945 and on his return took up his trade as an industrial chemist.
He was recruited from University Blacks as a brilliant full-forward, and was to earn his fame playing with the Melbourne Football Club as a centreman. He was captain of Melbourne during their hat-trick of premierships in 1939, 1940 and 1941. La Fontaine went on to coach Melbourne from 1949 until 1951.