Researchers find that teacher self-efficacy influences student performance and student academic interest (Anderson, Green & Loewen, 1988; Ross, 1992; Ashton & Webb, 1986; Woolfolk & Hoy, 1990; and Muijs & Reynolds, 2001) and that prior teaching and teacher preparation experiences influence teacher self-efficacy (Preito & Altmaier, 1994). Since the late 1990s, a significant number of teachers have been drafted to teach engineering content in secondary schools across America (NAE & NRC, 2009). Given that none of those teachers were specifically prepared for that task in pre-service secondary engineering teaching licensure programs, some—or perhaps even many—of these new secondary engineering educators might be experiencing low teacher self-efficacy, which research suggests would lead to relatively ineffective secondary engineering teaching. Thus, the purpose of this study was to investigate experiences/factors that might influence secondary engineering teachers' self-efficacy, to inform those who are developing new pre- and in-service secondary engineering teacher preparation programs, and educational administrators / policy-makers. The population of Project Lead the Way (PLTW) secondary engineering teachers across the U.S. was invited to participate in this study. PLTW offers the best-known secondary engineering curriculum in the U.S. It features robust linkages/articulation agreements with post-secondary engineering programs (McVearry, 2003). The data for this study were obtained by administering the Teachers' Self-Efficacy Belief System-Self (TEBS-S) instrument (Dellinger, Bobbett, Oliver, & Ellett, 2008) and a demographic instrument developed by the researcher. The following factors had a statistically significant influence on teacher self-efficacy: pre-PLTW teaching experience, PLTW teaching experience, post-secondary course hours completed, teacher licensure process, and current and past teaching schedules. Implications of these findings may be used by administrators and educators who are actively involved in recruiting, selecting and preparing secondary engineering educators.