Objective Military families face numerous changes and stresses as they negotiate deployments and other life transitions. How they cope with these events is an important part of their overall well‐being and resilience. This longitudinal study on coping in a sample of National Guard couples examined the association between the predeployment coping (active vs. avoidant) of each in the relationship, and their own and their significant others’ mental health (anxiety, depression, posttraumatic stress disorder [PTSD]) and family well‐being (dyadic adjustment and parenting stress) postdeployment. Method A total of 238 matched couples completed the predeployment survey, 143 matched couples completed the post, with 122 matched couples completing both pre‐ and postdeployment surveys. Results While active coping was not significantly associated with any outcomes, predeployment avoidant coping in both soldiers and significant others was associated with increased anxiety, PTSD, and depression post deployment (actor effects). Additionally, soldier avoidant coping predeployment was associated with increased parenting stress for soldiers, while significant other avoidant coping predeployment was associated with increased relationship distress for significant others (actor effects). Finally, significant other avoidant coping predeployment was associated with higher parenting distress for soldiers postdeployment (partner effect). Conclusion Findings suggest that interventions are needed to combat avoidant coping (behavioral disengagement, denial, substance abuse) predeployment because this way of coping is strongly related to negative outcomes. In addition, those who work clinically with these families should work to reduce avoidant coping strategies and any familial dynamics exacerbated by this way of coping.