Background Stroke is a disabling, long-term condition that challenges the mental and physical health of stroke-survivors concurrently with their primary family-caregivers (dyad). However, there has been a lack of emphasis on this dyadic need. Thus, this study aims to investigate the impacts of two interventions on hope, self-esteem and hedonic wellbeing on depression among the stroke-survivor–caregiver dyad. Methods This randomized-controlled-trial applied the actor–partner interdependence model to 100 randomly-selected dyads (N = 200) of stroke-survivors, mean (SD) age was 73.63(7.22) and family-caregivers, mean (SD) age was 62.49(14.44) years, recruited from Hong Kong hospitals and rehabilitation centres. The intervention was eight-weekly two-hour narrative therapy group sessions (n = 54 dyads), compared with the current model of psychoeducational group to each dyad as needed. Outcomes were collected via questionnaires and interviews, at four time-points: baseline (T1), during-intervention (T2) (1-month), immediately post-intervention (T3) (2-months) and follow-up (T4) (6-months). Results The results demonstrated that there are actor effects on stroke-survivors (β = −0.353, p < 0.05) and caregivers (β = −0.383, p < 0.05), where higher levels of hedonic wellbeing were associated with fewer depressive symptoms. Partner effects were observed as caregivers’ depressive symptoms were possessing a significant negative relationship with stroke survivors’ wellbeing (β = −0.387, p < 0.05). Those stroke survivors in the intervention group had a significantly higher level of self-esteem associated with lower levels of depression (β = −0.314, p < 0.05). Conclusions Improving hope, self-esteem and wellbeing through narrative therapy significantly mediates depressive symptoms, strengthening the dyadic support of stroke survivors and family caregivers.