U.S. Catholic parishes are steadily becoming more diverse. Seeking a theological basis for ecclesial unity in diversity, U.S. theologians and bishops have, over the past two decades, drawn heavily on post-Vatican II communion ecclesiology. The purpose of this article is to examine how the ecclesiology of communion has shaped contemporary pastoral approaches to diversity in the Roman Catholic Church in the United States. I contend that the failure of mainstream communion ecclesiology to confront structures of racism in church life has limited its adequacy as a model of ecclesial community in the contemporary U.S. context. Yet the ubiquitous ecclesiological model also contains the resources for its more critical retrieval by U.S. womanist and feminist theologians, who have done so by emphasizing difference over diversity and transposing the language of unity into the praxic key of solidarity.