Coral reefs are among the most biodiverse ecosystems on Earth with Great Barrier Reef (GBR) being the world's largest coral reef systems. Despite its ecological importance, there is limited understanding of the abundance and distribution of microplastics (MPs) in the GBR. For the first time, this study aims to quantify and characterize MPs in water (>25 µm) and MPs as well as nanoplastics (NPs) (> 0.5 µm) in sediment from six sites around the Heron Island. A total of 48 surface water, 27 inter-tidal sediment and 18 sub-tidal sediment samples were collected. Water samples were collected using a custom-built high-volume sampling device, while sediment samples were collected using transect (inter-tidal) and grab sampling (sub-tidal) approach. A comprehensive quality assurance and quality control (QA/QC) protocol was implemented during sampling, processing and analysis, to ensure data reliability. MPs in water ranged from 0.2 to 1.3 particles/L, predominantly as fragments (59.7%) and fibers (40.3%). The analysis of sediment samples is currently ongoing, with expected MP concentrations higher than in water. MP and NPs polymer composition is yet to be analyzed using Fourier Transform Infrared Spectroscopy (FTIR)/ Optical photothermal infrared (O-PTIR) spectroscopy. Results provide crucial data to assess the MPs contamination in GBR.