The present study examined the efficacy of a media literacy education, substance abuse prevention training workshop for late elementary school teachers. Analyses revealed that the randomly assigned intervention (n = 18) and control (n = 23) teachers were similar in demographic characteristics and pre-training beliefs and knowledge. Teachers who participated in the workshop reported stronger beliefs in the importance of and familiarity with media literacy education and scored higher on a direct assessment of media deconstruction skills than teachers in the control group. Teachers reported positive program assessment ratings. This randomized controlled trial provides evidence that a one-day teacher training workshop on media literacy education is effective at improving teachers' beliefs and knowledge about media literacy that are relevant for successful student outcomes.