The “Occurrences from the Alien CSI Bioblitz: citizen science to engage society in invasive species monitoring” dataset is an occurrence dataset published by the Research Institute for Nature and Forest (INBO) in collaboration with the AlienCSI COST (European Cooperation in Science and Technology, CA17122) research network (Roy et al. 2018). The dataset contains all the alien species data collected during the Alien CSI Bioblitz. This bioblitz was organized for the first time in May 2022 as a three day event and is planned to be repeated yearly. This bioblitz activity aims to engage society in invasive species monitoring. The first edition included guided bioblitzes in thirteen different protected areas across twelve European countries. The data are published as a standardized Darwin Core Archive. Issues with the dataset can be reported at https://github.com/alien-csi/bioblitz-occurrences/issues We have released this dataset to the public domain under a Creative Commons Public Domain Dedication. We would appreciate it if you follow the INBO norms for data use (https://www.inbo.be/en/norms-data-use) when using the data. If you have any questions regarding this dataset, don't hesitate to contact us via the contact information provided in the metadata.