ABSTRACT Background: A burn event can elicit symptoms of posttraumatic stress disorder (PTSD) in survivors and their partners and may impact the way these couple members interact with each other. They may try to protect each other from further emotional distress by avoiding talking about the burn event, but they may also show concern towards each other. Objective: The aim of this study was to investigate bidirectional relationships between survivor’s and partner’s PTSD symptoms and two interpersonal processes: partner-oriented ‘self-regulation’, which is avoidance-oriented, and ‘expressed concern’, which is approach-oriented. Method: In this longitudinal multi-centre study, 119 burn survivors and their partners participated. Measures of PTSD symptoms, self-regulation, and expressed concern were administered in the acute phase following the burns, and follow-ups took place up to 18 months postburn. Intra- and interpersonal effects were examined in a random intercept cross-lagged panel model. Exploratory effects of burn severity were also investigated. Results: Within individuals, survivor’s expressed concern predicted later higher levels of survivor’s PTSD symptoms. In their partners, self-regulation and PTSD symptoms reinforced each other in the early phase postburn. Between the two couple members, partner’s expressed concern predicted later lower levels of survivor’s PTSD symptoms. Exploratory regression analyses showed that burn severity moderated the effect of survivor’s self-regulation on survivor’s PTSD symptoms, indicating that self-regulation was continuously related to higher levels of PTSD symptoms over time within more severely burned survivors, but not in less severely burned survivors. Conclusion: PTSD symptoms and self-regulation reinforced each other in partners and possibly also in more severely burned survivors. Partner’s expressed concern was related to lower levels of survivor’s PTSD symptoms, whereas survivor’s expressed concern was related to higher levels of survivor’s PTSD symptoms. These findings emphasize the importance of screening for and monitoring PTSD symptoms in burn survivors and their partner and of encouraging couple’s self-disclosure.