Institutions and organizations have increasingly recognized the importance of fostering diversity and inclusion within their ranks. Nevertheless, translating these aspirations into tangible outcomes remains challenging. Increasing demographic diversity does not automatically lead to inclusion, and insufficient inclusion efforts can undermine the sustainability of diversity initiatives. This presentation aims to shed light on strategies that members of dominant groups can employ to actively promote diversity and inclusion through their interpersonal relationships. The presentation comprises two distinct but interconnected streams of research. First, I will present a series of studies exploring the concept of allyship as perceived and defined by LGBT+ individuals, as well as the myriad positive consequences associated with allyship. Second, I will discuss ongoing research centered on the role of faculty mentors and peers in supporting doctoral students pursuing careers in STEM (Science, Technology, Engineering, and Mathematics) fields. Drawing from a combination of qualitative, survey, and experimental research methodologies, this research reveals the importance of interpersonal behaviors in fostering inclusion for women and people of color in STEM fields. The findings from these two research streams collectively emphasize the pivotal role that individuals, particularly those from dominant groups, can play in championing diversity and inclusion within institutional and organizational settings.