ObjectivesThis qualitative study aimed to characterize how social networks influence cardiovascular health behaviors among U.S. South Asian adults in a culturally adapted, group lifestyle intervention. MethodsA purposive sample of participants (n = 24) from the South Asian Healthy Lifestyle Intervention (SAHELI) randomized trial’s intervention arm participated in semi-structured process evaluation interviews. Specific open-ended questions were used to probe participants’ behavior changes, personal social networks, and social support for behavior change. The team transcribed interviews and identified themes using inductive and deductive coding, based on a theoretical model of social influence. ResultsAmong 24 participants (67 % female, mean age 50.5 years, 88 % foreign-born, 50 % with limited English proficiency), three themes emerged: 1) SAHELI participants and their family members provided bidirectional social support for behavior change; 2) intervention participants provided social support to one another; and 3) participants faced resistance to change from some community members. ConclusionsBehavior changes initiated during SAHELI diffused to participants’ close family members. Several social network influences varied by participant gender, English language proficiency, and network member type. Practice ImplicationsHealth professionals should ask patients about how their social networks facilitate or hinder behavior changes. Gender and cultural factors may modify how social networks influence behavior change.