There are well documented links between close relationships and physical health, such that those who have supportive close relationships have lower rates of morbidity and mortality compared to those who do not. Inflammation is one mechanism that may help to explain this link. Chronically high levels of inflammation predict disease. Across the lifespan, people who have supportive close relationships have lower levels of systemic inflammation compared to people who have cold, unsupportive, and conflict-ridden relationships. Not only are current relationships associated with inflammation, but past relationships are as well. In this article, we will first review the literature linking current close relationships across the lifespan to inflammation. We will then explore recent work showing troubled past relationships also have lasting consequences for people’s inflammatory levels. Finally, we will explore developmental pathways that may explain these findings.