This study estimated the abundance of microplastics (i.e., plastics measuring less than 5mm) on marine turtle nesting beaches during 2018-08-04 to 2020-01-24. Samples were collected with metallic trowel. Sand samples were collected from 209 sites spanning six oceans and 39 countries by a global network of marine turtle scientists. Microplastics were extracted through stacked sieves, visually identified, and a sub-sample verified via Fourier-transform infrared spectroscopy. Microplastic particles were counted and weighed, which in combination with the dry sand sample weight and volume, allowed multiple units of measure to be calculated: Plastic weight per kg of dry sediment (g kg-1), plastic particle number per kg of dry sediment (particle kg-1), and plastic particle number per m-3 of dry sediment (particle m-3). Plastic particles were also categorized into five types: industrial plastic pellets, foams, fragments, sheetlike user plastics and threadlike user plastics. This dataset contains the results from all 209 samples in a spreadsheet format.