PurposeThe barriers to integrating sustainable practices into construction project management require extensive resource allocations to resolve. Within developing countries such as Iran (where resources are scarce), remedial strategies adopted must prioritise tackling those barriers that can be expected to yield maximum return on investment. The candidate barriers are many, and this paper aims to identify a hierarchy of barriers, providing a priority list of remedial targets.Design/methodology/approachA mixed philosophical stance of interpretivism and post-positivism is adopted within a deductive approach and survey strategy. A list of 30 known barriers are identified from extant literature and used to formulate a questionnaire data collection instrument administered within the Iranian construction industry. Data collected from 176 practitioners are analysed using the relative importance index and Mann–Whitney U test to compare groups based on the participants' demographic variables.FindingsThe findings challenge the common assumption that items related to market and workforce experience are major inhibitors of change. That is, economics and regulatory dependent barriers have a higher impact on the failure of a shift to sustainable practices in Iran. The most influential barriers to incorporating sustainability in construction projects are: (1) lack of understanding of the potential benefits; (2) insufficient cooperation among practitioners, research institutions and environmental organisations; and (3) a lack of a systematic approach to pursuing sustainability goals. No significant associations are detected between the affiliation of the respondents and their attitude towards the issue. Thus, a generalised approach can be applied to a broader range of organisations and construction projects in Iran.Originality/valueWhile studies on sustainability impediments at the firm or project level are ubiquitous within literature, this research identifies that the most significant barriers to sustainable project management in Iran, as an underexplored context, are those experienced at the economic and institutional level. Moreover, this novel research presents important insights into the potential effects of participants' demographic profiles on their view of the importance of identified barriers.