OBJECTIVES: Recent evidence has shown that young adults have poor knowledge about reproductive health and fertility, and that interventions are needed to increase fertility awareness. The aim of this study was to assess the effectiveness of a brief video in increasing knowledge about fertility and infertility in young adults. METHODS: We carried out a two-arm, parallel-group, randomised controlled trial with a pre-test/post-test design (NCT02607761, ClinicalTrials.gov). The sample was composed of 173 undergraduates who completed a self-report questionnaire. Participants were randomly assigned to exposure or no exposure to an educational video about reproductive health and infertility (intervention group, n = 89; control group, n = 84). RESULTS: At baseline, participants revealed poor knowledge of infertility risk factors and fertility issues, and average knowledge of the definition of infertility. Interaction effects between group and time were found for all variables targeted in the video. Participants in the intervention group significantly increased their knowledge of fertility issues, infertility risk factors and the definition of infertility. No significant differences in post-test knowledge were observed in the control group, except for the age at which there is a marked decrease in female fertility. CONCLUSIONS: A short video intervention is effective in increasing short-term knowledge about reproductive health and infertility. If future research using longer intervals corroborates our findings, video intervention could be a useful tool in public health prevention campaigns.