Parents are in a powerful position to teach sexual topics to their children, promoting positive sex attitudes and lifelong sexual health. However, parents may lack sexual knowledge and confidence to address such topics. This study, grounded in social learning theory, tested the effects of an active learning intervention to increase parental efficacy regarding sexual communication with children aged one- to five-years-old. Parents were randomly assigned to a control group (n = 55), a factsheet group (n = 58), and an active learning group (n = 56). Multi-level Modelling (MLM) analyses showed the intervention was not effective at increasing parental sexual communication efficacy. However, a dosage effect was observed for the active learning and factsheet groups. In addition, factsheet and active learning intervention groups showed significant gains in knowledge of child sexual development. The results of this study suggest active learning may be a step towards promoting lifelong sexual health.