This explanatory sequential mixed methods research study investigated motives and purpose exhibited by professionals transitioning from careers in science, technology, engineering and math (STEM) to secondary education. The study also analyzed personal perceptions of teaching preparedness, and explored barriers to successful teaching. STEM career changers were surveyed and interviewed. Study participants without industry experience and graduate degrees perceived themselves as being more prepared than study participants with industry experience and graduate degrees when developing lesson plans. Additionally, study participants without graduate degrees felt more prepared than those with graduate degrees in the area of classroom management. Overall, participants perceived themselves as most prepared in assessment and their content area and least prepared in classroom management and handling the psychological needs of their students. Specific recommendations for STEM alternative teacher education programs, instructors within these programs, and STEM career changers are included.