Synopsis With the rapid proliferation of technology, online learning has spread remarkably, proving its sustainability even in the field of teacher professional development (TPD). Oman, through its Ministry of Education (MoE), has adopted several online initiatives thus far. Although online TPD (OTPD) has spread markedly, little is known about the impact of such courses on Omani teachers. This study is aimed to address this gap in the research by investigating the experiences of Omani English teachers in one of the OTPD courses, Special Educational Needs (SEN). A qualitative approach was applied in the study: five Omani English teachers who participated in the online SEN course were interviewed. The content of the interviews was then analyzed using thematic analysis. The data generated was used to answer the research questions from the perspective of the social constructivism, based on the community of inquiry (CoI) framework. The results reveal that several factors affect teachers’ learning in the online SEN course. These factors are related to the three presences of the CoI framework: cognitive presence – content-based learning, critical thinking learning based on communication and reflection, and self-directed learning; social presence – interaction and communication; and teaching presence – course design, the e-moderator’s role, materials, and teaching methods. The findings also indicate that the teachers themselves play a crucial role in the success of their learning by being motivated and having positive attitude towards the course. The results also demonstrate that the teachers’ ability to transfer and sustain the knowledge gained depends on both private factors, such as their attitude, responsibility, and perception of online learning, interests, and needs; and public factors, such as supervision support, follow-up practices, school structure, and school culture and context