objective: investigate the prevalence of suspected cases of common mental disorders in a population assisted by one professional team of the brazilian family health program as well as to evaluate its associated factors. methods: a cross-sectional survey study was carried out using a randomized systematic sampling procedure for selecting 277 subjects from the target population. for data collection, two instruments were administered to the sample, the self report questionnaire (srq-20) as well as a sociodemographic questionnaire. results: the global prevalence of cases suspected of presenting common mental disorders in the target population was of 43.70%. females had a significantly higher prevalence rate (48.37%), when compared to males (34.41%). the variable "family income" had an inverse relation to the common mental disorders prevalence. the logistic regression analysis indicated that only two variables - "use of medication" and "family income" - were significantly associated to common mental disorders. conclusions: the results indicated a higher prevalence of common mental disorders in this target-population, compared to data from other similar studies, indicating the need for a special attention to be rendered by the primary health care system to detect and treat those cases in families attended by the brazilian family health program, specially those characterized by the associated factors detected.