Guillermo J. Dagohoy was born on October 23, 1919 in Sogod, Southern Leyte. His parents were Agustin Dagohoy and Macaria Jacobe. He had one brother, Hospicio, and three sisters, Celestina, Rufina, and Dulcesima.
Guillermo grew up in Sogod where he finished his elementary grades at Sogod Elementary School. In 1938, the family settled in Davao, and Guillermo continued his high school studies at Davao City High School. He attended college at the Visayas Institute, now the University of the Visayas where he finished with an Associate in Arts. He eventually became a high school teacher in the Assumption Academy of Peñaplata in Samal Island.