In the fall of 1988, faculty and students at the California Polytechnic State University at San Luis Obispo, California petitioned for a Pi Tau Sigma chapter. The petition was supported by Dean Peter Lee, Department Head Ronald Mussulman, and Professor Charles Black. On March 3, 1990 Cal Poly San Luis Obispo Phi Psi was officially installed by National President, Dr. James Welty, and National Secretary Treasurer, Dr. Edwin Griggs. Twenty five students were initiated as charter members and Dr. Don Chivens was initiated as an honorary member. Don Chivens assumed the role as the chapter advisor.
Initial activities of Cal Poly Phi Psi include providing of tutoring services for mechanical engineering students in conjunction with Tau Beta Pi. Participation in "Engineering Day" involves introduction of engineering to young students in the area. The goal is to try to spark an interest in engineering as a career.