The main objective of this study is to assess the impact of project management methodology (PMM) on project management success (PMS) of the construction industry in Sri Lanka by developing a new model to the existing body of knowledge and to contribute some practical aspects to the project management practitioners. Accordingly, the conceptual framework was developed with the theoretical support of the Contingency theory. The researcher-administrated questionnaires were distributed under a one-time survey strategy and 381 respondents were used for analysis. According to the nature of the study, the widely used Structural Equation Modelling technique (SEM) was used to analyze the data, and SmartPLS Version 3 was used as the tool found that all three project methodologies are impacting significantly on Project Management Success with Standard Project Management Methodology (SPMM) being the strongest followed by Customized Project Management Methodology (CPMM) and Inhouse Developed Project Management Methodologies (IPMM). The findings of this study show that 39% of the variation in project management success is explained by the project management methodologies.