The commitment of women to the principles and ideals of Alpha Phi Omega commenced within the first decade of APO in the Philippines. Typically, a fraternity chapter would have a soiree with the most prestigious sorority on its campus and this would then be closely followed by a joint service project. Once a cordial relationship had been established, the sorority would then affiliate with the fraternity chapter. In other chapters, the fraternity would found a sorority composed of their women friends. Thus, in the early years of Alpha Phi Omega in the Philippines it was not uncommon for different fraternity chapters to be associated with sororities bearing different names.
The Alpha Phi Omega National Board of Sorority was first adopted during the 6th National Biennial Convention held at the Mapua Institute of Technology, Manila on 6-7 March 1965. It was to exist under the national name of "Sigma Gamma Phi Sorority" and was to serve as the umbrella organization of all affiliated sororities of the collegiate fraternity chapters of APO Philippines. The women, who had at that time already formed strong partnerships with the fraternity chapters, recognized the need for greater unity and sought to integrating all existing affiliated sororities into one national sorority under the jurisdiction of the Alpha Phi Omega Philippines National Executive Board.
The officers who were elected by the sorority delegates to serve as the first National Board of Sorority were:
Based on archival material from different fraternity chapters, among the initial affiliated sororities that formed the foundation upon which the Alpha Phi Omega Sorority in the Philippines would emerge were:
In 1968, the APO National Executive Board passed a resolution changing the APO National Sister Sorority name from Alpha Phi Sigma Sister Sorority to Alpha Phi Omega Auxiliary Sorority, or APOAS. This resolution to change the Greek-letter name of the sorority and make it correspond with the name of the fraternity served to underscore their affiliation with APO Philippines. Consequently, this paved the way for the recognition of Alpha Eta's Auxiliary Sorority Chapter (PSBA Manila) on 17 September 1968, with Sis. Amelia P. Acuzar as the holder of Sorority ID #001.
The 7th National Biennial Convention held at Far Eastern University, Manila on 15-16 December 1968, adopted the said existing NEB resolution and officially allowed its collegiate fraternity chapters to admit women as affiliate members.
During the 8th National Biennial Convention held at the University of the Philippines, Los Baños, Laguna on 17-19 December 1971, the Sorority was formally recognized and accepted as Alpha Phi Omega Auxiliary Sorority (APOAS), the sister organization of the Alpha Phi Omega Service Fraternity.
However, the name suggested a dependence on the fraternity, and so the women of Alpha Phi Omega sought to have their equal status recognized and for them to carry their own identity. Thus, during the 10th National Biennial Convention held from 30 March to 1 April 1979 at Camp 7, Minglanilla, Cebu, the National Code of By-laws was amended and the Alpha Phi Omega Service Sorority (APOSS) came into being. It was also during this convention that the Office of the Vice President for Sorority Affairs was created, which gave the women of APO Philippines the recognition of the equal and distinct status they aspired to and deserved. Consequently, the national organization became the Alpha Phi Omega International (Philippines) Incorporated Service Fraternity and Sorority.