Positivity resonance (i.e., shared moments of positive affect, mutual care, and behavioral synchrony) is theorized to contribute to a host of positive outcomes including relationship satisfaction. The current study examined whether behavioral indices of positivity resonance (rated using a new behavioral coding system) in long-term married couples are associated with concurrent shared positive affect using a well-established dyadic-level behavioral coding system (i.e., Specific Affect Coding System: SPAFF), and whether positivity resonance predicts concurrent marital satisfaction independently from shared positive affect and individual-level positive affect. Long-term married couples completed a self-report inventory assessing marital satisfaction and were then brought into the laboratory to participate in a conversation about an area of marital disagreement while being videotaped for subsequent behavioral coding. Inter-rater reliability for positivity resonance behavioral coding was high (interclass correlation coefficient: 0.8). Results indicate that positivity resonance is associated with shared positive affect using SPAFF. Additionally, positivity resonance predicted marital satisfaction independently from SPAFF-coded shared positive affect and individual-level positive affect alone. These findings provide preliminary construct and predictive validity for positivity resonance behavioral coding, and highlight the role positivity resonance may play in building relationship satisfaction in long-term married couples.