Microplastics (plastics < 5mm in length) are widespread and persistent contaminants of concern in marine ecosystems. To manage this environmental problem, it is crucial to gather spatial and temporal data on microplastic presence, quantity, and characteristics. The Australian Institute of Marine Science (AIMS) and the Integrated Marine Observing System (IMOS), supported by the National Collaborative Research Infrastructure Strategy, have established the New Technology Proving Marine Microplastics Monitoring Program (NTP-MMMP) to monitor for microplastics in Australian marine waters. During 2021 and 2022, and supported by an extensive IMOS field operation, more than 160 surface seawater samples were collected from seven locations (Darwin, Yongala Shipwreck, Port Hacking, Bonney Coast, Gulf Saint Vincent, Spencer Gulf, and Rottnest Island) and analysed by AIMS to determine the presence, abundance, and characteristics of microplastics and other anthropogenic debris. After stringent QA/QC, the microplastics data has been made publicly available via the Australian Ocean Data Network (AODN). This talk summarizes the (1) field and laboratory workflows applied, (2) lessons learnt throughout the NTP-MMMP, and (3) preliminary analysis of the dataset. The relevance of the AODN dataset to assess environmental risks of marine microplastic contamination is also discussed.