Sustainable transport, such as using inland waterway transport (IWT), represents a major pillar of the European Green Deal to reduce global warming. To evaluate the different inland transport modes (road, rail, IWT), it is crucial to know the external costs of these modes. The goal of this paper is a critical review of external cost categories (e.g., accidents, noise, emissions) and external cost calculation methods of IWT to provide ideas for future research. We identified 13 relevant papers in a literature review dealing with external costs of IWT. In a meta-analysis, the papers were assigned to the seven external cost categories: accident, noise, congestion, habitat damage, air pollution, climate change and well-to-tank emissions. The most investigated external cost categories are climate change, air pollution and accidents. Two studies were identified as the major external cost calculation methods for IWT in the abstract. Our paper shows that the data basis of IWT is significantly lower than for road/rail. The measurement of energy consumption and related emissions of IWT needs to be qualitatively and quantitatively improved and brought up to the level of road traffic, to ensure an accurate comparison with other modes of transport.