"False consensus" refers to individuals with (v. without) an experience judging that experience as more (v. less) prevalent in the population. We examined the role of people's perceptions of their social circles (family, friends, and acquaintances) in shaping their population estimates, false consensus patterns, and vaccination intentions. In a national online flu survey, 351 participants indicated their personal vaccination and flu experiences, assessed the percentage of individuals with those experiences in their social circles and the population, and reported their vaccination intentions. Participants' population estimates of vaccination coverage and flu prevalence were associated with their perceptions of their social circles' experiences, independent of their own experiences. Participants reporting less social circle "homophily" (or fewer social contacts sharing their experience) showed less false consensus and even "false uniqueness." Vaccination intentions were greater among nonvaccinators reporting greater social circle vaccine coverage. Social circle perceptions play a role in population estimates and, among individuals who do not vaccinate, vaccination intentions. We discuss implications for the literature on false consensus, false uniqueness, and social norms interventions.