It is now well established that nature and nurture are both important contributors to variation in human personality. As a result, the field of personality behavior genetics is moving beyond simply estimating the magnitude of genetic and environmental influences on various personality constructs. Recent methodological advances provide for the study of how these different sources of influence interact in the development of personality. Specifically, newer biometrical moderation models allow for group-specific estimates of heritability and environmental influences on personality (a form of gene–environment interaction). In the current paper, we review selected recent research using these models. Furthermore, we explore how moderation might also be important in understanding links between specific genes and personality. Accounting for the contingencies between genes and environment will be an important catalyst for the molecular genetic study of personality, as unmoderated ‘main effect’ types of gene → personality associations have been elusive.