PurposeThis study aims to first identify influencing factors of outsourcing decisions in construction projects systematically and further to unravel the interactions of these influencing factors from a holistic perspective.Design/methodology/approachThis study concerns the design and analysis of two-stage studies, where, at the first stage, a systematic literature review and 48 semi-structured interviews with senior practitioners in construction firms were conducted to identify influencing factors in outsourcing decisions in construction projects. At the second stage, the decision-making and trial evaluation laboratory (DEMATEL) method was employed to explore the interactions between influencing factors and pathways of outsourcing decisions.FindingsThree focuses for outsourcing decisions are outlined, revealing that outsourcing restrictions, strategic needs and cost objectives need to be considered in outsourcing decisions. In addition, the finding contributes to the integration of transaction costs perspective and capability perspective by unravelling the mechanism of how different factors work together.Practical implicationsThis study outlines 18 influencing factors and three sequential focuses for outsourcing decision-making, providing a clearer understanding of each factor’s contribution for decision-makers.Originality/valueMost of the existing studies stressed the net effect of individual outsourcing factors from a single logic and paid little attention to their complex causal relationship. This study develops a holistic perspective of the influencing factors of outsourcing in construction projects by contending the overall knowledge of outsourcing and analyzing the causal relationship between them.