Invasive species - New Zealand pigmyweed (Crassula helmsii) occurrences in Flanders, Belgium is a sampling event dataset published by the Research Institute for Nature and Forest (INBO). It contains information on 274 sampling events with 162 occurrences of invasive New Zealand pigmyweed starting from 2013. This dataset is a subset of a larger vegetation analysis and focuses only on the Crassula helmsii occurrences. Here the dataset is published as a standardized Darwin Core Archive and includes for each event: a stable eventID, date and location of the observation, and a short description of the sampling protocol (in the event core), supplemented with specific information for each occurrence: a stable occurrenceID, the scientific name and higher classification of the observed species, the number of recorded individuals and a reference to the observer of the record (in the occurrence extension). Issues with the dataset can be reported at https://github.com/inbo/data-publication/issues We have released this dataset to the public domain under a Creative Commons Zero waiver. We would appreciate it if you follow the GBIF citation guidelines (https://www.gbif.org/citation-guidelines) 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 or via https://twitter.com/trias_project. This dataset was published as open data for the TrIAS project (Tracking Invasive Alien Species http://trias-project.be, Vanderhoeven et al. 2017), with technical support provided by the Research Institute for Nature and Forest (INBO).