Objectives <p>Individuals in established relationships often report problems with their sexual well-being, including feeling sexually dissatisfied, experiencing low sexual desire, or feeling worried or concerned about their sex life. Cross-sectional and experimental research find that mindfulness—present-moment awareness without judgment—is associated with greater sexual well-being (i.e., high sexual satisfaction, high sexual desire, and low/absent sexual distress). However, most research has focused on trait mindfulness rather than sexual mindfulness—mindfulness during sex—despite evidence that sexual mindfulness is related to sexual well-being over and above trait mindfulness. Research is further limited in that few studies have accounted for the interpersonal context of sex, sampling individuals, rather than couples. Further, no studies have employed a daily experience design which is necessary to capture fluctuations in sexual mindfulness across sexual encounters. The current study addressed these critical limitations by examining associations between daily sexual mindfulness and sexual well-being in a community sample of couples (<i>n</i> = 297 couples).</p> Methods <p>Each partner independently completed validated measures of sexual mindfulness and sexual well-being via an online survey over 35 consecutive days.</p> Results <p>On days when individuals had sex and were more sexually mindful (compared to their own average across all days), both they and their partners reported higher sexual satisfaction, higher sexual desire, and lower sexual distress that day.</p> Conclusions <p>Findings from this research add to the growing body of literature supporting sexual mindfulness as a factor associated with both intra- and interpersonal sexual well-being benefits in couples. Strategies that increase an individual’s ability to be present and non-judgmental during sex may promote greater sexual well-being for oneself and one’s partner over the course of their relationship.</p> Preregistration <p>The study was preregistered on the Open Science Framework (<a href="https://doi.org/10.17605/OSF.IO/4KZG9">https://doi.org/10.17605/OSF.IO/4KZG9</a>). </p>