The Arctic environment is transforming rapidly due to climate change. Aerosols’ abundance and physicochemical characteristics play a crucial, yet uncertain, role in these changes due to their influence on the surface energy budget, and aerosol properties are also changing in response. Despite their importance, year-round measurements of such characteristics are sparse in the Arctic and often confined to lower latitudes at Arctic land-based stations and/or during short high-latitude summertime measurements campaigns. Here, we present the unique aerosols microphysics and chemical composition datasets collected in the central Arctic Ocean during the year-long Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. These datasets, which include aerosol particle number concentrations, size distributions, cloud condensation nuclei concentrations, fluorescent aerosol concentrations and properties and aerosol bulk chemical composition (black carbon, sulfate, nitrate, ammonium, chloride and organics) will serve to greatly improve our understanding of high-Arctic aerosol processes, with relevance towards improved modelling of the future Arctic (and global) climate.