Background : During cancer, coping strategies adopted by patients with prostate cancer and their spouses have an effect on their own emotional state and quality of life (QoL). However, the effects of coping strategies used by a member of a couple on the well‐being of the other member are unknown. The aim of this study is to examine the dyadic effects of coping strategies on the emotional state and QoL of couples dealing with cancer. Methods : Ninety‐nine couples completed various self‐questionnaires to assess psychological and physical QoL, anxiety, depressive symptoms, and coping strategies at the beginning, middle, and end of primary treatment. Results : Results obtained with the actor–partner interdependence model showed that coping strategies used by patients or spouses play a key role not only in their own well‐being but also in their partners'. Indeed, when patients use problem‐focused coping or social support‐seeking, they, as well as their spouses, experience fewer anxiety and depressive symptoms. Conversely, patients or spouses who use emotion‐focused coping experience higher levels of anxiety and depressive symptoms. Finally, and it is a surprising result, when spouses seek social support, patients feel greater anxiety. Conclusions : These findings suggest that both patients and spouses should be included in psychosocial programs, which develop and reinforce their ability to cope with cancer. Couples may benefit from membership in support groups allowing them to share their experiences.