On December 6, 1845, Louis Manigualt, Stephen Ormsby Rhea, and Horace Weiser met at Yale University to form the organization that ofAlpha Sigma Phi. This society was formed to unite the standards and principles that the three young freshmen sought to preserve through brotherhood. As the nation's eleventh oldest men's fraternity, Alpha Sigma Phi has endured a long history of following the goal “to better the man.” 

From the Alpha Tau chapter of Alpha Sigma Phi at Stevens Institute of Technology sprang a Little Sister program. This program saw the offspring of two sororities, Delta Phi Epsilon and Omicron Pi. The Little Sister program of Alpha Sigma Phi was instrumental in gathering a group of females with common interests and promoting a fraternal system between them. 

In January of 1987, the current sisters of the Alpha Sigma Phi saw a need to be more independent. This group of eight women, (Dawn Marie Ablett, Vibhuti Amin, Michelle Brassard, Magella Luna, Rosemarie Maffei, Melissa Martin, Kathy Marcinak and Agnes Olszewska) met on Saturday, January 11, 1987 to draft a constitution. They then approached the administration of Stevens Institute of Technology and the current undergraduate governing body, STUCO. Both organizations agreed with the need for independence and so, Omicron Pi became an officially recognized student organization at the institute. 

At the next regular meeting of the Inter-Fraternity Council (IFC) in March of 1987, Omicron Pi was nominated a pledge sorority. As a pledge member of IFC, Omicron Pi was extended rush privileges. By then, two of the founding sisters had graduated, which left six to carry on. The Alpha Class of five women pledged in October of 1987 and became sisters on February 15, 1988. In March of 1988, the IFC voted to extend Omicron Pi the full privileges of a sorority.