IMCS would play an important role in the development of Ecumenical and Inter-religious dialogue. Following the World War II, IMCS developed strong relationships with the World Student Christian Federation (WSCF). Some of the IMCS Inter-Federal Assemblies (IFAs) were held in conjunction with the WSCF and for a number of years in the 1960s, the North American Secretariat was a joint office of WSCF, IMCS and ICMICA.

In 1959, IMCS and ICMICA held a historic meeting in Manila under the auspices of UNESCO on "The present impact of the Great Religious on the lives of Men in the Orient and Occident." This was attended by Hindus, Buddhists, Shintoists, Muslims, Jews, Orthodox, Protestants, and Catholics. This meeting was one of the first formal meetings sponsored by Catholics and with the approval the Vatican, that brother together so many different religious leaders.