Multiracial organizing since the 1980s has centered around the need to define and make visible the term multiracial (e.g., U.S. Census). In the contemporary era when multiple race populations are a growing and institutionally recognized demographic, how do multiracial organizations characterize and seek to combat collective experiences of racial marginalization? Here, we draw on in-depth interviews with officers from diverse multiracial organizations in the U.S. and Canada (N = 19) collected from 2017 through 2018 to examine this question. The findings revealed that multiracial individuals experience distinct forms of exclusion, which we call categorical invisibility, that target individuals who do not “fit” into established monoracial categories, and mixture as pathology, a less common frame but representing more overt forms of bias targeting those of mixed backgrounds. The lived impacts of these experiences prompt the expressed need for “safe” spaces from the psychosocial costs of categorical invisibility. Multiracial organizations, located mostly in the United States with one in Canada, engage in diverse community building and advocacy efforts to address these needs and, thus, represent critical sites of resistance to the trauma of racial (in)visibility. This work amplifies the need to center Critical Multiracial Theory to expose how monoracial paradigms as a central feature of White supremacy continue to shape the lives of multiracial people and expand our knowledge on how multiracial organizations shape the (re)negotiation of racial categories that challenge the racial status quo.