The objective of this study is to investigate whether project complicatedness and the chances of recurring exchanges influence the adoption of relational transactions in public construction projects. A structured questionnaire was administrated in Singapore. The Partial Least Square-Structural Equation Modelling was used to analyze the data. The statistical results show that: (1) the level of project complicatedness has a positive correlation with the preservation of relationships, cooperation between contracting parties and procedural flexibility; and (2) the chances of recurring exchanges are positively correlated with harmonization between contracting parties, cooperation between contracting parties and procedural flexibility. The quantitative results were complemented by qualitative evidence from eight in-depth interviews, which validated that both the level of project complicatedness and the chances of recurring exchanges have influence on the adoption of relational transaction practices. This study contributes to knowledge by presenting empirically that project characteristics influence the adoption of relational transactions.