Extension educators are increasingly using flipped classrooms, wherein online content delivery precedes in-person learning. We have applied this approach to two Extension programs in which citizen scientists are trained in early detection of invasive species. Our goal in using the tool of flipped classrooms is to accommodate large amounts of content while focusing classroom time on skills development. In 2017, we assessed efficacy of the flipped classroom through knowledge tests and surveys completed by 174 participants and 106 participants, respectively. Results demonstrated large knowledge gains and high participant satisfaction. We encourage Extension professionals to consider whether use of the flipped classroom format could advance achievement of their programs' learning objectives.