This study explores the professionalism of English as a Foreign Language (EFL) teachers in secondary schools by examining the extent to which Teacher Professional Development (TPD) programs impacted their professionalism based on their perceptions, and the constraints they encountered. Using purposive sampling, qualitative data were collected through interviews with two English teachers at Pesantren Darul Ihsan as the participants. Data were analyzed using Braun and Clarke’s thematic analysis. The findings revealed that workshops and webinars are the most likely TPD programs they undertake. These TPD activities significantly improved the teachers' self-efficacy, confidence, classroom practices, instructional skills, and reflective competence, enhance student engagement and participation. Teachers reported feeling more confident in addressing classroom challenges, which improved their overall teaching effectiveness and created a more dynamic learning environment. However, several challenges were also identified, including time constraints, a lack of contextual relevance in some programs, insufficient resources and institutional support, and the theoretical nature of certain TPD activities. These barriers limited the teachers' ability to fully engage with and implement the strategies learned, highlight the need for more practical, context-specific, and supported professional development programs.