Background: Although sexual arousal is commonly experienced in the daily context of relationships, most of what we know about sexual arousal comes from studies on individuals, often conducted in a laboratory context. Aim: To explore to what extent similarity in levels of sexual arousal during non-genital physical intimacy (i.e., cuddling and kissing) was associated with each partner’s affect, as well as their sexual and relationship satisfaction. Methods: Ninety-four cohabitating couples (M age = 26.30, SD = 7.60; 88 mixed-gender, 6 same-gender) completed six ecological momentary assessments a day for ten consecutive days. We used response surface analysis to examine the associations among the degree and direction of similarity in partners’ sexual arousal and affective, sexual, and relational outcome variables. Outcomes: Sexual satisfaction, relationship satisfaction, positive and negative affect. Results: Sexual arousal levels covaried only when partners engaged in physically intimate behaviors, unlike affective responses, which covaried also within couples more globally over time. Within-couple similarity at high levels of sexual arousal was positively associated with women’s sexual satisfaction, but unrelated to men and women’s relationship satisfaction and affect. Individual- and couple-level sexual arousal was positively associated with men’s sexual satisfaction and with women’s sexual and relationship satisfaction. Couple-level sexual arousal was relevant to men’s affect, such that positive affect was higher when sexual arousal levels within the couple were high. Our analyses also revealed a discrepancy effect, in that women’s positive affect was higher when their own sexual arousal levels were higher than that of their partner. Clinical Implications: These findings suggest that as long as sexual arousal levels within a couple are sufficiently high, both sexual arousal similarity and discrepancy can be beneficial to one’s well-being, supporting the relevance of therapeutical techniques aimed at increasing arousal levels to promote better affective and relational climate for couples. Strengths & Limitations: This study is the first to test the daily associations among sexual arousal similarity and its correlates in a sample of cohabitating couples, providing a more comprehensive view of the interpersonal dynamics through which sexual arousal may influence individual, relational, and sexual well-being. Given our sample’s relatively young age, as well as high sexual and relationship satisfaction, the results may not generalize to couples experiencing sexual or relational distress. Conclusion: Within the context of daily relationships, individual- and couple-level dynamics of sexual arousal were associated with sexual and relationship satisfaction, as well as with affective responses of relationship partners.