Guided by evolutionary game theory (Korte, Koolhaas, Wingfield, & McEwen, 2005), this study aimed to identify the genetic precursors and the psychosocial sequelae of inhibited temperament in a sociodemographically disadvantaged and racially diverse sample (N = 201) of 2-year-old children who experienced elevated levels of domestic violence. Using a multimethod, prospective design across 3 annual measurement occasions, the authors conducted structural equation modeling analyses indicating that trained observer ratings of inhibited temperament at age 2 were uniquely predicted by polymorphisms in dopamine and serotonin transporter genes. Children's inhibited temperament, in turn, indirectly predicted decreases in their externalizing problems at age 4 through its association with greater behavioral flexibility at age 3. Results highlight the value of integrating evolutionary and developmental conceptualizations in more comprehensively charting the developmental cascades of inhibited temperament.