This study addressed teachers' perceptions of the effect of online teacher professional development programs (OTPDPs) on their professional development. This five-month study focused on four aspects of OTPDPs: (1) Teachers' perceptions on OTPDPs, (2) the impact of OTPDPs on lesson planning, (3) the impact of OTPDPs on STEM teaching, and (4) the impact of OTPDPs in STEM education on teacher employment. The sample consisted of 36 teachers. An OTPDP tailored to STEM education was designed to help participants develop professional skills. This study adopted a qualitative type of research, which was a single case study." Data were collected through interviews, videotapes, and lesson plans. The data were analyzed using content analysis. Participants had positive perceptions about OTPDPs. They stated that the OTPDP helped them plan and teach STEM better and gain pedagogical and content knowledge. It also allowed them to acquire technological self-efficacy. They also noted that OTPDPs helped teachers develop the skills that would make them more likely to be employed in the future. The results indicate that technological self-efficacy and Internet access are of paramount importance for effective OTPDPs.