In a context where video has become commonplace in formal and informal learning, video annotation tools, which enable users to annotate shared video content for private or collaborative use, have received a growing interest in education. We critically review literature that reports on the use of video annotation with particular emphasis on the relationship that video annotation has with the chosen instructional use of video, the features offered by the selected annotation tool, the processes it enables, and the learning outcomes. Applying a State-of-the-Art review methodology, our search resulted in 205 records that were analyzed, with 26 eligible studies meeting all the inclusion criteria. Overall, 20 studies reported positive learning outcomes, two reported negative learning outcomes, and four studies reported no learning outcomes. The analysis of the video annotation tools that were used in the selected studies indicates that some features are available in most tools (like sharing or tagging annotations) whereas some features (like the possibility to add hyperlinks or videos in the annotations) are fairly uncommon. Such analysis also allowed us to provide a comprehensive definition of 'video annotation', still lacking in the literature. In the discussion we raise some methodological and conceptual issues that should be addressed in future research and provide specific guidelines for the choice of video annotation tool.