The aim of this study was to examine associations between the importance of religion and disclosure of HIV seropositivity within sero-nonconcordant couples. In 2003, a face-to-face survey was conducted among patients selected in a random stratified sample of 102 French hospital departments delivering HIV care. Respondents who reported being in a couple with a non-HIV-positive partner were asked whether they had disclosed their HIV positive status to their partner and if religion represented an important aspect of their life. Among the 2,932 respondents, 1,285 were in a sero-non-concordant regular partnership. Among these, 37.5% reported that religion played an important role in their life; 7.2% had not disclosed their HIV-positive status to their partner, and 11.6% were unaware of their partner's HIV status. Lack of HIV-disclosure to the partner was encountered more often among those who considered religion as an important aspect of their life. After multiple adjustment for socio-demographic factors, and for partnership characteristics, the importance of religion in the respondent's life remained independently associated with a lack of HIV-disclosure to the regular partner. In conclusion, individuals who place importance on religion appear to have difficulties in disclosing their HIV-positive status due to the associated stigma and fear of discrimination.