As people who cross racial boundaries in the family formation process, the experiences of interracial couples can actually reveal the nature of racial boundaries within and across societies. I draw on in-depth qualitative interviews with eighty-seven respondents in interracial Black and White couples in Los Angeles and Rio de Janeiro to compare perceptions of public stigmatization by outsiders, a term I call “boundary-policing.” I find that couples in Los Angeles perceive gendered, Black individuals as perpetrators of this boundary-policing. In Rio de Janeiro, couples perceive regionalized and classed, White perpetrators. These findings suggest that in the United States and Brazil, racial boundaries are intertwined with class and gender boundaries to shape negotiation of boundary-policing in the two contexts. This analysis builds on previous studies of ethnoracial boundaries by showing how individuals reinforce and negotiate them through interpersonal relations. It demonstrates the similarities and differences in the negotiation and reinforcement of racial boundaries in the two sites.