The contamination of aquatic environments by microplastics has been largely documented in the last years, especially in oceans, rivers, and lakes, but their occurrence in remote mountain lakes has been scarcely considered. This work aims to investigate the presence and abundance of microplastics and fibres in a remote, alpine, and uninhabited lake in Switzerland (Sassolo). In this study, the water column as well as the sediments were analysed. The isolation of microplastics and fibres from the samples of the sediment was achieved with a digestion process using H₂O₂ and a density separation technique with NaI. Classification of microparticles (from 5 mm to 125 μm) was first developed with an optical microscope. Infrared spectroscopy was then used to identify and characterize the chemical nature of the microplastics and fibres. On average, 2.6 microplastics and 4.4 fibres per litre were identified in the water column. On the other hand, the results of the sediment samples revealed significant fibre concentrations compared to plastic microparticles (514 fibres and 33 microplastics per kilogram). The most abundant types of microplastic identified in the samples were composed of polyethylene (PE) and polypropylene (PP). Microplastic and fibre sources were not determined, but it is likely that the number of human activities in this area as well as aerial deposition are contributing to contaminate this remote environment with microplastics and fibres.