Family interventions have been emphasized in the treatment of bipolar disorder (BPD) due to the bidirectional and entangled relationships between patients and the family system, and have benefits for patients’ symptoms and health; however, the effects of family interventions on family function and caregivers’ health‐related outcomes have not been well investigated. This randomized, controlled trial with 47 hospitalized patients with BPD/family caregiver dyads at a medical centre in northern Taiwan compared the effects of a brief family‐centred care (BFCC) programme with treatment as usual (TAU). All of the family caregivers in two groups were invited to attend a routine 60‐min family discussion group about violence and suicide prevention. The TAU group without specific family interview for patient and family caregiver dyad. In the BFCC group, four 90‐min BFCC programme sessions were additionally provided twice a week for each hospitalized family dyad. We hypothesized that, first, family caregivers in the BFCC group could increase their family function, and second, improve perceived health status and reduce caregiver's burdens compared to the TAU. The results showed that family caregivers in the BFCC group significant interaction effects in overall family function (P = 0.03) and subscale conflict (P = 0.04), communication (P = 0.01), and problem‐solving (P = 0.04), but there were no significant interaction effects on the caregivers’ perceived health status and caregivers’ burdens. Our findings support both the feasibility of using the BFCC programme for inpatients and its specific benefits for family function. An intensive family intervention during hospitalization has been suggested in psychiatric practice to support patients with BPD and family caregivers.