The authors examined the associations of the Big Five personality factors with religiousness in adulthood for a 19-year longitudinal sample of 492 adolescents age 12 to 18. Among the Big Five, Conscientiousness in adolescence was uniquely related to higher religiousness in early adulthood. For adolescents high in Emotional Stability, the link between strength of religious upbringing and religiousness in adulthood was weaker than it was for adolescents who were less emotionally stable. These findings replicate the work of others demonstrating the importance of Conscientiousness as a predictor of religiousness and suggest that emotionally unstable adolescents might be more likely to adopt levels of religiousness that are similar to those of their parents.