Given the high symptom burden and low survivability of lung cancer, patients and their spouses have been found to experience poor mental health. The current study examined the roles of dyadic appraisal and dyadic coping on the mental health of 78 couples living with non-small cell lung cancer. Multilevel modeling revealed that spouses, on average, reported significantly worse mental health than patients. Dyadic appraisal and dyadic coping played important roles in predicting mental health, controlling for known developmental and contextual covariates. Dyadic appraisal of the patient’s pain and fatigue was significantly associated with spouse mental health, albeit in opposite directions. Dyadic coping significantly predicted patient mental health. The study underlines the need to incorporate routine screening of both patient and spouse mental health, and highlights the complex role of appraisal within the couple in a life-threatening context. Viewing the couple as a unit, rather than separate individuals, raises important awareness about the role of disparate illness appraisals and coping strategies within the dyad on the health of both members. Nurses are particularly well situated to engage in a collaborative family-focused approach to the couple with cancer that promotes communication and health.