This paper is an attempt to explore the barriers to integrating sustainability into construction project management in developing countries. To this end, a comprehensive review of the literature is conducted, as a result of which a
list of 30 barriers is culled from existing studies. The list of barriers is subsequently assessed in terms of relative importance index (RII) through a survey questionnaire administered to Iranian construction industry experts, resulting in
a dataset of 176 completed questionnaires. Findings bring to light the most influential barriers to incorporating sustainability in construction projects for a developing country. These were: (1) lack of understanding of the potential selfbenefits of proactivity and high economic risks that unsustainable practices may carry, (2) inadequate assessment of
risks and a silo-based approach, namely, insufficient cooperation among practitioners, research institutions and environmental organisations and (3) the lack of a systematic approach to planning and acting for the fulfilment of sustainability goals. As one of the first studies in its kind, the paper offers invaluable insight for researchers, practitioners, and
policy makers, in supporting the transition of construction project management practices towards fulfilling sustainable
development goals.