Born in Gardenville, Pennsylvania, Fullam graduated from Villanova University with a Bachelor of Science degree in 1942.

He was the Democratic candidate for the U.S. House of Representatives from Pennsylvania's 8th District in the 1954 and 1956 elections but was defeated by Karl C. King and Willard S. Curtin, respectively.

On January 19, 1966 President Lyndon Johnson nominated Fullam to the Eastern District, to a seat vacated by Judge Abraham Lincoln Freedman.

They commissioned the architect Paul Rudolph to design a home for their family in Wrightstown, Pennsylvania.

John Fullam died on March 8, 2018, at Plush Mills Senior Living in Wallingford, Pennsylvania.