The purpose of this study was to explore the effect of support groups on caregivers' knowledge and social support. A quasi-experimental pre-post control group design was used in this study. Eight weeks of psychoeducational support groups served as an intervention. There were three waves of data collection: pre-test, post-test, and one month during follow-up. A total of 70 caregivers with schizophrenic patients were assigned into experimental and control groups with 35 persons each. The result of the study showed that the knowledge of disease and social support significantly improved in the experimental group compared with those of the control group. The improvement remained significant at the end of first month during follow-up. Social support showed a tendency to decrease with time but was still improved over pretest. Recommendations based on the results of this study include: (1) caregiver support groups should be promoted as a conventional mode of care; and (2) training in support group theory and practice and in group leadership should be incorporated into continuing education programs, to upgrade nurses' ability to lead support groups.