In an effort to address K-8 teacher confidence in STEM and increase basic genetics knowledge to a level consistent with its importance in society, we have developed, implemented, and evaluated a 7-day teacher professional development workshop. The overarching goal of our workshop is to facilitate the implementation of innovative DNA-based classroom activities in K-8 classrooms by (i) increasing teacher content knowledge, (ii) increasing teacher confidence in teaching STEM, and (iii) developing teacher interest in using engaging activities, so they are empowered to teach new content in compelling ways. We relied on case-based learning to provide relevance and context to scientific content that was not initially familiar to many of the teachers. Here we describe the workshop and its evaluation. Overall results suggest positive gains in teacher learning, confidence, and interest in the scientific content, as well as the intention to incorporate the scientific content and activities into their teaching.