Higher education has been a key pillar of every country's development with its purpose being to develop the scientific, technological, cultural, economic, political, and social dimensions of society. It is obvious that reaching this purpose requires engaged faculty members. Whenever they have high engagement, they can create or increase the engagement in their students as well. In this study, faculty members’ engagement for teaching, researching, and social activities has been considered giving rise to this question: what are the factors affecting work engagement decline of faculty members of public universities in Iran? Due to the nature of the study, qualitative research was conducted. Participants were 22 faculty members of public universities of Tehran who were selected by the purposive sampling method and were interviewed in an in-depth and semi-structured manner until theoretical saturation was reached. Then, using thematic analysis the text of each interview was coded regularly and the themes and concepts were identified and categorized into 3 main themes, 8 sub-themes and 18 conceptual categories and discussed. According to the findings, structural barriers, content barriers, cultural barriers, negative tendencies, negative dynamics, barriers related to students, community, colleagues, and dean reduce the work engagement of faculty members of public university in Iran. Exploring the declining factors of faculty members’ work engagement, this research enjoys specific novelty and offers suggestions for resolving or controlling them.