The shortage of certified science, technology, engineering, and mathematics (STEM) teachers is of concern throughout the United States because of significant numbers needed over the next over the next 10 years. Addressing this issue in education, this study examined the experiences of three new STEM teachers who entered teaching through different pathways, focusing on those experiences related to the effectiveness of mentoring and the meaningfulness of professional development. Based on three case-study analysis, the findings provide an insight into the importance of mentoring and professional development for STEM teachers during their induction year to promote teacher persistence in the profession. This article provides ideas for recruitment, instructional preparation, and STEM teacher retention practices. (Contains 2 tables.)