Cost-benefit analysis (CBA) is the most commonly used economic assessment tool for transport infrastructure investments. There are radically different approaches to its use across the world, highlighting the need for local research. While CBA is extensively reported on in many countries, an Australian perspective is less commonly found. This study aims to provide an Australian perspective on the use and efficiency of CBA in transport infrastructure investment assessments. It examines the guidelines used in practice and the CBA of real-life transport projects in relation to the costs and benefits considered in CBA and the CBA as a tool to inform investment decision making. This study identified the implications for wider CBA use, including the practical issues that should be addressed in guidelines and the challenges of implementing CBA outcomes in investment decision making. Improving CBA practices and assessments of transport infrastructure investments contributes to ensuring that investment decision making is well-informed.