Objective The present study examines the impact of parents' perceptions of child‐related stress on observed couple communication and their self‐reported relationship satisfaction. Background A considerable body of evidence indicates that challenges related to raising children can negatively affect parents' interactions and relationship satisfaction. Although some potentially underlying mechanisms have been explored in previous research, questions about the potential effect of child‐related stress on the interparental relationship remain open. Method Parents' perceptions of child‐related stress and relationship satisfaction were assessed in a convenience sample of 118 parental couples living in Switzerland. Additionally, the couples participated in a conflict conversation task to obtain an observational measure of couples' communication quality. Data were analyzed with an actor–partner interdependence mediation model. Results Child‐related stress among parents was directly linked to lower relationship satisfaction in both partners and one partner's child‐related stress was associated with the other partner's communication quality. The mediation analysis revealed that high levels of child‐related stress were linked with relationship satisfaction by impairing the other partner's communication quality. Conclusion The study suggests that child‐related stress is among the challenges that may impair parents' relationship quality, partially mediated through worsened couple communication. Implications The findings support the potential benefits of prevention programs aimed at reducing child‐related stress and enhancing couple coping skills for maintaining parents' relationship satisfaction over time.