Sustainability is one of the most important challenges of our time. Projects play a pivotal role in the realization of more sustainable business practices and the concept of sustainability has also been linked to project management. However, how managers of projects consider sustainability in their operational daily work is still to be explored. This paper uses Q-methodology to investigate the consideration of sustainability aspects in the decision making processes of project managers. The research question was How are dimensions of sustainability considered in the decision-making processes of project managers in relation to the triple constraint of time, cost and quality? Based on the Q-sort of selected respondents, the study found that the consideration of sustainability principles is underrepresented, compared to the triple constraint criteria. However, the analysis of the individual Q-sorts revealed four distinct perspectives that differ significantly in their consideration of sustainability principles and triple constraint criteria. •The integration of sustainability in project management is picking up momentum, however, more empirical research is needed.•Integration of sustainability into project management requires consideration of a holistic set of sustainability principles, rather than a set of indicators.•In decision making in projects, consideration of sustainability principles is underrepresented, compared to the triple constraint criteria.•The study revealed four distinct perspectives that differ significantly in their consideration of sustainability principles and triple constraint criteria.