Research has established that mindfulness may be useful to individual and dyadic well-being among both early-stage and long-term relationships. Nonetheless, it remains unclear which mechanisms of mindfulness are most relevant to relationship satisfaction among long-term married couples. Furthermore, although previous research suggests that an individual’s total mindfulness is not related to his or her partner’s relationship satisfaction, we have yet to determine whether any specific facets of mindfulness may evidence a significant cross-partner association with relationship satisfaction. The present study seeks to address these gaps in the literature using the Five Facet Mindfulness Questionnaire (FFMQ). Data were collected from 164 long-term married couples (M relationship length = 28.30 years, SD = 8.43 years). Hierarchical linear modeling indicated that one’s Nonjudgment of Inner Experience uniquely predicts one’s own relationship satisfaction above and beyond the other facets, and that an individual’s Nonreactivity to Inner Experience uniquely predicts his or her spouse’s relationship satisfaction above and beyond the other facets. Implications for utilizing mindfulness aimed at both intra-individual and cross-partner relationship enhancement will be discussed.