Background: The consequences and high costs of psychiatric disorders impact family caregivers greatly. Health services should identify and provide accessible support programs to facilitate effective caregiver coping.; Purpose: The aim of this study was to determine the effectiveness of a theory-of-planned-behavior-based problem-solving training program on the coping styles of family caregivers of psychiatric inpatients.; Methods: In this two-group, randomized control trial, 72 family caregivers were randomly assigned to either a control group receiving standard care or an intervention group receiving a training program (eight sessions over 4 weeks). Demographic information was recorded at baseline, and the Coping Inventory for Stressful Situations was administered to both groups at baseline, immediately postintervention, and 1-month follow-up.; Results: Immediately after the intervention, the intervention group earned significantly higher task-oriented coping style scores (mean difference = 5.03, p = .015) than the control group, but no significant difference was detected between the two groups for either emotion- or avoidance-oriented coping style scores. At 1-month follow-up, the intervention group earned significantly higher scores than the control group for task-oriented (mean difference = 8.56, p < .001) and emotion-oriented (mean difference = 7.14, p = .002) coping styles. No improvement in avoidance-oriented coping style at the postintervention or follow-up time points was detected.; Conclusions: Implementation by nurses and other health professionals of problem-solving training programs that are based on the theory of planned behavior is recommended to strengthen the use of task- and emotion-oriented approaches that help family caregivers of psychiatric patients better cope with stress.