There is growing evidence that inflammatory responses may help to explain how emotions get “under the skin” to influence disease susceptibility. Moving beyond examination of individuals’ average level of emotion, this study examined how the breadth and relative abundance of emotions that individuals experience— emodiversity—is related to systemic inflammation. Using diary data from 175 adults aged 40 to 65 who provided end-of-day reports of their positive and negative emotions over 30 days, we found that greater diversity in day-to-day positive emotions was associated with lower circulating levels of inflammation (indicated by IL-6, CRP, fibrinogen), independent of mean levels of positive and negative emotions, body mass index, anti-inflammatory medications, medical conditions, personality, and demographics. No significant associations were observed between global or negative emodiversity and inflammation. These findings highlight the unique role daily positive emotions play in biological health.