This study aimed to understand the relationship between caregiver culture and infant pain expression at the 12-month immunization and discern if a mechanism subsuming this relationship was the quality of caregiver behaviors (emotional availability). Infants (N = 393) with immunization data at 12 months of age were examined. On the basis of the Development of Infant Acute Pain Responding model, a mediation model was developed to examine how caregiver behaviors mediate the relationship between caregiver heritage culture and infant pain. Culture was operationalized by an objectively derived quantification of caregivers' self-reported heritage culture's individualism. Two mediation models were estimated, examining infant pain expression at 1 and 2 minutes post-needle. Caregivers who self-reported heritage cultures that were more highly individualistic tended to show greater emotional availability, which in turn predicted decreased infant pain expression at 1 and 2 minutes post-needle. The present findings further our understanding of one mechanism by which caregiver culture affects infant acute pain expression. PERSPECTIVE Adding to the literature examining direct relationships between culture and infant immunization pain, this article proposes the quality of caregiver behaviors as a mechanism by which culture affects infant acute pain expression at 12 months of age. Results support the proposed mechanism and inform our understanding of the role of caregiver culture in the infant pain context.