In this article, we examine the distribution of a marker of immune system stimulation—C‐reactive protein—in urban Brazil. Social relationships are associated with immunostimulation, and we argue that cultural dimensions of social support, assessed by cultural consonance, are important in this process. Cultural consonance is the degree to which individuals, in their own beliefs and behaviors, approximate shared cultural models. A measure of cultural consonance in social support, based on a cultural consensus analysis regarding sources and patterns of social support in Brazil, was developed. In a survey of 258 persons, the association of cultural consonance in social support and C‐reactive protein was examined, controlling for age, sex, body mass index, low‐density lipoprotein cholesterol, depressive symptoms, and a social network index. Lower cultural consonance in social support was associated with higher C‐reactive protein. Implications of these results for future research are discussed.