Objective: To test the hypothesis of an association between knowledge and sexual risk behaviours (SRB) among community-clinic workers in Chile, explained by the confounding effect of self-perceived vulnerability to HIV. Methods: Analysis of a cross-sectional survey, nested within a quasi-experimental study of 720 community-clinic workers in Santiago. The SRB score combined number of sexual partners and condom use, coded as “high”/“low” SRB. The Knowledge of HIV, a 25-item index, was coded as “inadequate”/“adequate” knowledge. Self-perceived vulnerability to HIV was categorised as “high”/“moderate”/“low”. Control variables included socio-demographics, educational level, and occupation. Descriptive, association and confounding analysis was developed through proportions/averages, Chi-square tests, and logistic regression (OR-estimations). Results: Respondents were 78,2% female, 46,8% married, 67,6% Catholic, mean age 38,9 years(d.s.=10.5), 69% had University/Diploma level and 58,7% reported occupational risk of HIV. An adequate level of Knowledge (75% sample) was associated with educational level (OR=2.5,CI=1.7-3.4) and occupational risk (OR=3.3,CI=2.2-5.0). Self-perceived vulnerability was “low” in 71,5% cases. A negative association between Knowledge and SRB was found (OR=0.55,CI=0.35–0.86), but Self-perceived vulnerability did not have a confounding effect on this relationship. Conclusions: Some community-clinic workers had inaccurate knowledge of HIV, which was associated to SRB. Self-perceived vulnerability did not have a confounding effect, however, future studies should further analyse occupational risk of HIV as possible driving factor in health workers´ perception of their risk. Focused training programmes should be developed to enhance basic knowledge of HIV in this group