Background Many factors are believed to shape an individual’s religious/spiritual beliefs and behaviours (RSBB) as part of their wider social behaviour, including psychological traits such as intelligence, personality and social cognition. To explore these patterns further, we examined associations between multiple psychological factors and RSBBs in the offspring and parental generations of the Avon Longitudinal Study of Parents and Children (ALSPAC). Methods Three RSBB outcome measures were assessed – religious belief (belief in God/a divine power; yes/not sure/no), religious affiliation (Christian/none/other) and religious attendance (frequency of attendance at a place of worship) – in approximately 4,400 offspring (aged 28 years), 12,000 mothers and 9,500 of their partners from a prospective birth cohort study in Southwest England (ALSPAC). We explored age-adjusted (and sex-adjusted for offspring) associations between various psychological factors and each of the RSBB outcomes using multinomial regression. These psychological factors included intelligence/cognitive ability, personality, social cognition, locus of control, prosociality and self-esteem. Exposure-sex interactions were also examined for offspring, and exposure-age interactions for parents. Results Many psychological factors were associated with RSBB in this cohort, although relationships sometimes differed between cohorts or by RSBB outcome. For instance, in both offspring and mothers, intelligence scores were negatively associated with religious belief and affiliation, but positively associated with religious attendance. An external locus of control was negatively associated with religious belief and attendance in mothers and partners, but little association with religious belief was found in the offspring generation. Some age- and sex-interactions were reported. Most pseudo-R 2 values were below 0.5%. Conclusion Psychological factors are associated with RSBB in this population, although they explain relatively little of the variation in RSBB. Results are correlational, but suggest that associations between psychological factors and RSBB are present, and can be explored in more detail in future work to assess whether these relationships are causal.