|Prior literature has demonstrated the importance of sexual well-being (e.g., sexual satisfaction, functioning, desire) and relationship satisfaction for physical, psychological, and relational well- being. Therefore, it can be distressing for the many couples who experience declines in sexual or relationship well-being. According to theoretical and empirical research, sexual communication is an important interpersonal factor for sexual and relational well-being. However, one aspect of sexual communication has largely been neglected—sexual talk (communication occurring during sexual encounters). There are two types of sexual talk: individualistic (i.e., statements of dominance, submission, sexual ownership, and sexual fantasies; self-focused) and mutualistic (i.e., statements of excitement/pleasure, feedback/compliments, instruction, and bonding/intimacy; sharing/partner-focused). My dissertation examined how sexual talk was associated with sexual and relationship well-being for long-term couples and examined potential moderators. I conducted one cross-sectional study with individuals and two studies (one cross- sectional, one daily diary) with a new sample of couples. At higher perceived partner responsiveness (i.e., partner’s response is perceived as accepting, understanding, validating, and caring; PPR) greater mutualistic and individualistic talk was associated with less sexual distress and greater sexual satisfaction (respectively), whereas at lower PPR, greater mutualistic and individualistic talk was associated with more sexual distress and lower sexual satisfaction (respectively; Study 1). In Study 2, I found no gender/sex differences in sexual talk, although exploratory analyses with gender/sex diverse (GSD) couples suggested possible gender/sex and dyad type differences for individualistic talk. In Study 3, I found on days a person used more sexual talk, they reported greater sexual satisfaction (women only) and sexual desire, and their partner reported greater sexual satisfaction and (for individualistic talk only) sexual desire; exploratory analyses with GSD couples revealed potential differences from the binary couples. Overall, findings support the continued investigation of sexual talk in long-term couples, as it appears to be associated with sexual and relationship well-being for both members of a couple. Importantly, gender/sex and PPR demonstrated promise as moderators for when sexual talk is linked to greater sexual and relationship well-being. Interventions targeting sexual talk may facilitate greater sexual and relational well-being for long-term couples, who often face declines in these areas.