Projects are set up for specific purposes which are to be achieved within a stipulated time period, but not all projects achieve it set objective within the set time. In order for a construction project to be executed successfully, a team has to work closely together and implement project goals. All project stakeholders including the sponsor and the project implementation team are responsible for the successful completion of any project. This study, therefore, seeks to investigate organisational behaviours necessary for successful completion of a construction project. The study was conducted in Gauteng Province, South Africa and a structured questionnaire was administered to construction professionals. Retrieved questionnaires were analysed using the relative importance index. Findings from the study revealed that efficient relationship management, proper documentation of progress and effective teamwork are the most important traits required from project stakeholders to ensure successful completion of projects. It was, therefore, concluded certain behavioural traits must be inherent in project stakeholders and team members for a project to reach successful completion.