Social and personality psychologists aim to “understand individuals in their social contexts for the benefit of all people” (Society for Personality and Social Psychology, n.d.). Though this mission is admirable, value statements do little, on their own, to create an inclusive, high-quality science that benefits humanity broadly. In this research, we evaluate relationship science, a major subfield of social–personality psychology, illustrating both the unique diversity-relevant challenges faced by particular subfields and the barriers to inclusive and diverse research that are shared across research areas. Specifically, we examine the sample diversity and reporting practices of 1,762 studies published in eight mainstream psychology and relationships journals at two time points—(a) 1996–2000 and (b) 2016–2020—and center our analysis around five focal sample characteristics: gender, sexual orientation, regional context, socioeconomic status (SES), and race. We find that reporting practices and representation have not improved for some core demographic characteristics (e.g., socioeconomic status) and that even in domains for which reporting practices have improved (e.g., sexual orientation), reporting remains limited. Further, we find that reporting practices in relationship science frequently center Whiteness (e.g., “participants were mostly White”), obscure or overlook potential sexual orientation diversity (e.g., implying that individuals in man–woman dyads are “heterosexual”), and treat the United States as the contextual default (e.g., participants came from a “large Southeastern university”). In light of these findings, we offer recommendations that we hope will cultivate a more representative and inclusive discipline.