Floating photovoltaics (FPV) and high-altitude PV installations are increasingly gaining importance in the sustainable energy sector, each technology holding its own potential. A pioneering high-altitude FPV installation in Switzerland represents the first implementation of combining the two technologies. In order to determine the environmental performance of such an installation, the present study examines the life-cycle environmental impact of the world’s first high-altitude FPV system, using Life Cycle Assessment (LCA). Our results record life-cycle greenhouse gas emissions of 94 g of CO2–eq per kWh of electricity produced by the high-altitude FPV system. The non-renewable primary energy demand amounts to 10′810kWh oil-eq/kWp, which equals an energy payback time of 2.8 years. Environmental hotspots in the life cycle of the installation were found to be the production of the PV panels, due to the wafer production, and the mounting system, dominated by the production processes of the aluminium. Comparison to other PV installations identifies the mounting system as the main point of issue in the high-altitude FPV installation, due to a more intensive aluminium use. It was found that the high-altitude FPV installation can generally compete with alternative PV systems in the lowland, with its environmental impacts lying in the range of −45 % and + 15 %, while being largely outperformed by ground-mounted PV installations at high altitude. By implementing measures such as transitioning to renewable energies in the PV panel and mounting system supply chains, as well as reducing aluminium use for the mounting system, FPV systems hold great potential to help meet the increasingly growing demand of renewable energy sources.