The aims of this study were: (i) to assess the impact of caring for patients with schizophrenia on the mental health status of the caregivers; and (ii) to examine the direct and buffer effects of social support on the mental health status of these caregivers. A total of 61 key caregivers of patients with schizophrenia were administered the Chinese Health Questionnaire (CHQ) and the Measure of Support Function (MSF) self-report questionnaire to assess their mental health and social support status. The MSF questionnaire constitutes four subscales, including: (i) the perceived crisis support (PCS); (ii) the perceived routine support (PRS); (iii) the received crisis support (RCS); and (iv) the received routine support (RRS) subscale. The Positive and Negative Syndrome Scale (PANSS) was used to assess the psychopathology severity of the patients they cared for. Then the authors used the hierarchical multiple regression model to analyze the relationship between these variables. The psychopathology severity of the patients reflected by the PANSS scores correlated inversely with the caregivers' CHQ scores. Besides, the PCS subscale scores correlated positively with the caregivers' CHQ scores. Moreover, the interaction between the RCS subscale scores and the PANSS scores was significant. Significant positive correlation between the RCS and CHQ exists only in the higher PANSS subgroup, but not in the lower PANSS subgroup. The psychopathological severity of the patients has a negative impact on their caregivers' mental health. PCS has a direct effect, and RCS has a buffer effect on the mental health status of these caregivers.