This study looks at the critical success factors (CSFs) affecting integration of sustainability into project management practices of construction projects in developing countries. Having innovation diffusion theory as the theoretical point of departure, CSFs pertaining to the triple bottom line of sustainability (environmental, social and economic) were identified through a comprehensive review of literature. These were customised for the context of developing countries by conducting 16 semi-structured interviews and were presented in form of a conceptual model. The model was validated through a survey returning 101 completed questionnaires with partial least squares structural equation modelling (PLS-SEM) as the method of analysis. This study contributes to the field by presenting one of the first studies in its kind focusing on CSFs for integration of sustainability into project management practices for construction projects within the context of developing countries.