Established in 1907, the Rikkyo University Alumni Association serves all undergraduate and graduate program alumni. Its goal is to facilitate mutual friendship among its members and to contribute to the financial development of Rikkyo University. It currently has more than 200,000 members.

The main activities of the Rikkyo Alumni Association center on organizing alumni-related events such as the annual Homecoming Day festivities. It also publishes the quarterly newsletter St. Paul that is distributed to all alumni members. The Association also confers scholarships on currently enrolled students.

St. Paul's House was built in 1977 through the fundraising efforts of the Association's members. It provides a meeting venue for class reunions and the alumni clubs, and serves as the faculty restaurant.

There are 160+ domestic chapters and 30 overseas chapters.