This study examines the beliefs and practices regarding performance assessment among Korean English teachers in secondary schools. A survey was conducted with 109 teachers using a 52-item online questionnaire to investigate the extent to which teachers' beliefs align with their instructional practices and to categorize them based on these criteria. Although teachers acknowledge the pedagogical advantages of performance assessment, a significant gap exists between their beliefs and actual implementation, primarily due to the considerable time required for its execution. Teachers with longer tenure and higher qualifications demonstrated a more positive and effective application of performance assessment. The findings highlight the necessity for targeted professional development to enhance teachers' use of performance assessment strategies, especially for those who are skeptical about their effectiveness. Such initiatives are essential for bridging the gap between beliefs and practices, fostering an environment that promotes the effective use of performance assessment, and ultimately improving teaching quality and student learning outcomes in Korean English education.