This study examines the disconnect between the beliefs and practices of English for Specific Purposes (ESP) instructors regarding formative assessment in Hormozgan, Iran. Through classroom observations, semi-structured interviews, and a questionnaire, it was found that teachers espouse frequent use of formative assessment techniques but do not consistently implement them in practice. The research highlights the significance of instructors' beliefs in shaping their teaching methodologies and calls for a better understanding of formative assessment to enhance student learning outcomes.