Objectives Cancer not only affects the patient but also the partner. In fact, couples may react as a unit rather than as individuals while coping with cancer (i.e., dyadic coping). We assessed (1) the relationship between dyadic coping and relationship functioning in couples coping with cancer and (2) whether intervention studies aimed at improving dyadic coping were able to enhance the relationship functioning of these couples. Recommendations for future studies are provided. Method A systematic search was conducted to identify all eligible papers between January 1990 and September 2012. The databases P ub M ed, Psyc INFO , the Cochrane Library, and EMBASE were screened. Results Most studies ( n = 33) used an appropriate study design, adequate measurements, adequate analytical techniques, and a sufficient number of included participants to answer addressed research questions. However, the definition and assessment of dyadic coping strategies differed, which hampered comparison. Coping styles characterized by open and constructive (cancer‐related) communication, supportive behaviours, positive dyadic coping, and joint problem solving were related to higher relationship functioning, whereas dysfunctional communication patterns (e.g., protective buffering, demand–withdraw communication), unsupportive behaviours, and negative dyadic coping were related to lower relationship functioning. The results of the intervention studies were inconsistent: while some studies reported a beneficial effect on relationship functioning, other studies report no such effect, or only found a positive effect in couples with fewer personal relationship resources. Conclusions This review showed that adequate dyadic coping may improve relationship functioning, while dysfunctional dyadic coping may impede relationship functioning. In order to increase the comparability of the reported findings, a more uniformly conceptualized perspective on dyadic coping is needed. A better understanding of the dyadic challenges couples coping with cancer may face and more insight on how to expand the dyadic coping of these coupes might facilitate improvements in the quality of cancer care. Couple‐based intervention studies may increase the couples’ relationship functioning. However, future research is needed to examine more specifically which couples may benefit from such interventions. Statement of contribution What is already known on this subject? Dyadic coping may influence the distress experienced by both members of the couple and their relationship functioning. Several reviews already reported on the potential of couple‐based interventions to improve the dyadic coping of couples coping with cancer and on the beneficial effects of this coping on the psychosocial adjustment and relationship functioning of patients and partners (e.g., Badr & Krebs, ; Martire, Shulz, Helgeson, Small, & Saghafi, ; Regan et al ., ). However, even though we now know that couple‐based intervention might be useful, no systematic review has been conducted that focuses specifically on the mechanisms of dyadic coping itself. What does this study add? This review showed the importance of stress communication, supportive behaviours, and positive dyadic coping for the maintenance or enhancement of relationship functioning in couples coping with cancer. In addition, the dyadic intervention studies send an important message that encourages to further examine the potential benefit of such interventions in future. However, more consensus in the conceptualization and assessment of the dyadic coping styles is needed in order to increase the comparability of the reported findings.