This data publication is a database of published estimates of nitrogen, phosphorus, and carbon content of decomposing coarse detritus though time in freshwater ecosystems worldwide. Nutrient content measurements are paired with estimates of detrital mass loss within decomposition time series (i.e., defined cohorts of decomposing material through time) with the goal of understanding patterns and drivers of temporal elemental dynamics of freshwater detritus. A systematic literature search for aquatic decomposition experiments conducted on 29 April 2020 generated 580 records (after trimming for duplicates and obvious relevance). From this literature pool, we extracted 810 decomposition time series and associated environmental data (e.g., temperature, water quality, detrital characteristics). Time series included in this synthesis include a range of detritus types (including terrestrial and aquatic plant material, carcasses, dung, and veneers), ecosystems (including streams, lakes, rivers, and wetlands), and settings (including natural ecosystems, field mesocosms, and laboratory microcosms).