Previous studies have shown an inverse association between offspring religiosity and suicidal ideation/attempts, but the association of parent religiosity on offspring suicidal ideation/attempts has not been examined. To examine associations of parent and offspring religiosity with suicide ideation and attempts in offspring. The study is based on offspring (generation 3) from a 3-generation family study at New York State Psychiatric Institute and Columbia University, in which generations 2 and 3 were defined as being at high risk or low risk for major depressive disorder because of the presence or absence of major depressive disorder in generation 1. The association between suicidal behaviors (ideation/attempts) and parent and offspring religiosity in generation 3 offspring aged 6 to 18 years (214 offspring from 112 nuclear families) was examined. Parents' psychiatric diagnoses and suicidal behaviors were assessed with the Schedule for Affective Disorders and Schizophrenia, and offspring were independently assessed using the child version. Two measures of religiosity were assessed: religious importance and religious attendance. Logistic regressions in the framework of generalized estimation equations were performed to analyze offspring suicidal behaviors while adjusting for sibling correlation and offspring age, sex, and familial depression risk status. Of 214 offspring, 112 (52.3%) were girls. Offspring religious importance was associated with a lower risk for suicidal behavior in girls (odds ratio [OR], 0.48; 95% CI, 0.33-0.70) but not in boys (OR, 1.15; 95% CI, 0.74-1.80) (religiosity by sex interaction, P = .05). Religious attendance was associated with a lower risk for suicidal behavior in girls (OR, 0.64; 95% CI, 0.49-0.84) but not boys (OR, 0.94; 95% CI, 0.69-1.27) (religiosity by sex interaction, P = .17). Parent religious importance was associated with a lower risk for offspring suicidal behavior (OR, 0.61; 95% CI, 0.41-0.91) but not parent religious attendance. When parent and offspring religious importance were considered simultaneously, we found a lower risk associated with parental religious importance (OR, 0.61; 95% CI, 0.39-0.96) independent of offspring importance. These associations were independent of parental depression, marital status, and parental suicide ideation. In this study, parental belief in religious importance was associated with lower risk for suicidal behavior in offspring independent of an offspring's own belief about religious importance and other known parental factors, such as parental depression, suicidal behavior, and divorce.