This is a cross-sectional study conducted with 537 family caregivers of people with mental disorders. The objective was to quantify the degree of burden experienced by men and women, and identify the most affected dimensions of their lives and the factors associated with burden manifestation by gender. The Zarit Burden Interview (ZBI) scale was used to assess burden. Mean burden was 22.8 points (SD = 6.3) for men and 27.8 points (SD = 17.8) for women. The most affected dimensions among the two groups were the same; however, among the 22 items on the scale, 11 presented significantly higher means among women. The factors associated with the manifestation of burden in both groups were as follows: low income; use of psychotropic drugs; greater degree of dependence of the service user; not receiving family support; and dissatisfaction with family relationships. For men, manifestation of burden was also associated with age. For women, there were further associations of the outcome with the presence of health problems, not having someone to share care with, and caring for the assisted person for >10 years. Our findings suggest that the degree of burden of family members caring for those with mental disorders is associated with gender, and this should be considered by services responsible for planning care shared by professionals and relatives. Guidelines for Strengthening the Reporting of Observational Studies in Epidemiology (STROBE Statement) were adhered to in this study.