Phi Delta Gamma originated from a high school fraternity, Alpha Iota Omega, which was founded in 1939.

The founding brothers are Gilberto Oliver Padilla, Otis Oliver Padilla, Raúl Romaguera, Ramón Antonio Frontera, Ignacio Beauchamp, José Ramón Ponce de León, Hilton Quintana, Angel Inserni, Rafael Ferrer Monge “El Cubano” (who also developed the shield, the first rulebook, and the motto of the fraternity), Rubén D’Acosta, Edgardo Olivencia, César Arana and Hernán Rodríguez.

They began the task of establishing the Beta chapter in the University of Puerto Rico in Río Piedras.

Some of the founding brothers of the Beta chapter are Oscar Colón, Juan Mari Brás, Jean García, Ramón Vargas, Manuel Portela Lomba and Angel Amézaga.

Above all, the great brotherhood among its members is very characteristic of their family activities (which involve grandparents, parents, spouses, children, grandchildren, and even great-grandchildren).