Mathile graduated at age 16 from Portage High School, ranking first in his class of 14 students. He also lettered in basketball and earned an honorable mention for the all-state team. He went on to attend Ohio Northern University in Ada, Ohio, where he also played on the basketball team. He initially studied mechanical engineering before transferring to the business school. When an expected scholarship fell through, Mathile took a job pumping gas. Mathile graduated a quarter early in February 1962 with a business degree.
On July 7, 1962, he married MaryAnn Maas, the girl he had dated since high school. They have five children and live in Brookville, Ohio.
