In the present article, we investigated the relation between socio-demographic variables and personality factors with religious fundamentalism (RF). Our data were collected from a sample of 125 Italian Catholic participants (40 males, 85 females). Correlation analyses showed a significant association between RF and the openness domain of personality (negative pole), including both facet scales (openness to experiences and openness to cultures). We also found a significant association between RF and conscientiousness (only including the scrupulousness facet). Regarding socio-demographic variables, we found significant correlations between RF and years of education, church attendance, belief, and age, while there was no significant correlation between RF and gender. Path analysis showed that the effects on RF of socio-demographic factors are stronger than those of personality factors.