The association between socioeconomic status (SES) and physical health is robust. Yet, the psychosocial mediators of SES-health association have been studied in relatively few investigations. In this chapter, we summarize and critique the recent literature regarding negative emotions and cognitions, psychological stress, and resources as potential pathways connecting SES and physical health. We discuss the psychosocial origins of the SES-health links and outline how psychosocial factors may lead to persistently low SES. We conclude that psychosocial resources may play a critical mediating role, and the origins of the SES-health connection are apparent in childhood. We offer a blueprint for future research, which we hope contributes to a better understanding of how SES gets under the skin across the life span.