This study examines the relationship between project complexity and project success in construction projects in Ghana while assessing the moderating role of project management competencies (PMC). Using a quantitative cross-section research design, data was collected from 141 respondents in organizations that undertake construction projects in Ghana. Responses were analyzed using IBM SPSS (v.23.0) and Smart PLS 3.0. The results established a negative relationship between Technological, Organizational, and Environmental complexity and project success. Technological complexity was seen as the dimension of complexity that significantly affects the success outcomes of projects. PMC’s moderating influence was insignificant. The findings suggest that for projects to have an increased success rate, organizations must thoroughly investigate the kind of project complexity expected to be present in the project, and this will inform decisions on the caliber of skills/ competencies needed for a successful execution of the project.