In recent years, LGBT + communities have obtained significant victories in terms of recognition and civil rights in Western countries. Nonetheless, various forms of discrimination are still common, and a wide extent of variation is observed in societal attitudes towards LGBT + people. Several reasons may explain this heterogeneity, including religion. This work proposes a novel measure of tolerance towards LGBT + people, i.e. the Queer Friendliness Index, based on microdata drawn from a survey of citizen perception in Italy. Subsequently, we analyse the effect of active religious participation on the degree of tolerance towards LGBT + communities. To address self-selection among parish members, we resort to the Heckman procedure. We find that religious participation, reinforcing traditional values and creating strong relational ties among parish members, distorts the marginal effects of the socio-economic determinants of tolerance, producing an adverse effect. This problem may explain the large territorial differences observed across Italian macro-areas.