Anger-related problems have been documented among post-deployed service members who returned home, posing risks to their well-being and increasing distress in their families. Trait mindfulness (acting with awareness, nonjudging, and nonreactivity) has been associated with lower self-reported anger. Using actor–partner interdependence models, we tested the association between trait mindfulness and parental anger observed in parent–child and couple interactions. The sample consisted of 155 dyads of male National Guard/Reserve members who had been recently deployed and returned, and their female non-deployed partners. Results showed that fathers’ and mothers’ nonreactivity was negatively associated with their own observed anger, indicating that parents who reported higher nonreactivity exhibited lower anger. Mothers’ nonreactivity was also negatively associated with observed fathers’ anger in the same family such that fathers exhibited lower anger when their female partner reported higher nonreactivity. Nonreactivity facilitates emotion regulation and its cultivation may reduce anger in post-deployed military families.