Teachers’ job satisfaction and teacher self-efficacy in teaching are two of the main factors driving STEM teacher shortages in teaching students who are English Learners (ELs). This study investigated the impact of teachers’ perceptions of school climate and professional development (PD) participation on teacher self-efficacy in teaching and job satisfaction for STEM teachers of ELs. The public dataset TALIS 2018, including 985 public middle school STEM teachers of ELs in the USA, was used for the path analysis. The results showed that PD participation in multicultural education and STEM teachers’ perceptions of school climate had significantly positive direct effects on job satisfaction and self-efficacy in teaching ELs. Additionally, findings showed that STEM teacher self-efficacy in teaching mediates the relationship between school climate and teachers’ job satisfaction. This study contributes to the body of knowledge based on developing the capacity of STEM teachers of ELs and provides recommendations for future STEM teacher PD programs.