Guided by the limited previous literature of adolescent sexual debut and father behaviors, this study examined the influence of father warmth, involvement, and monitoring on adolescent age of sexual debut and likelihood of sexual debut before age 16. Participants and measures were drawn from the Flourishing Families Project and included 346 families and variables from measures completed by adolescents and their parents. A zero-inflated Poisson model was used to test the relationship between father variables and adolescent sexual debut. Gender differences were also analyzed. The findings indicate that an increase in father warmth correlates with a decreased age of sexual debut for adolescent sons and daughters. Results also suggest that an increase in father engagement is related to an increase in the age of debut. However, this variable was also associated with increasing the likelihood of debut for adolescent sons. No significance was found between father monitoring and the age or likelihood of debut. Findings suggest that father variables, independent of mother behaviors, uniquely influence adolescent sexual debut; these effects seem to be protective in some circumstances, while increasing risk in other instances. Implications for future research is considered.