We ran a leaf litter decomposition experiment over a seven-week period in each of three different years: 2017, 2018, and 2019. To assess leaf decomposition rates, we incubated leaf packs of freshly abscised Tabonuco (Dacryodes excelsa) leaves in pools in each of our two study stream reaches, and retrieved them at intervals over a seven-week period. We attempted to run experiments before onset of heavy rains which often occur in September-December. We chose to use leaves of Tabonuco for experimental leaf packs because it is a dominant riparian tree species along both of our study reaches. This dataset can be used to asses ecosystem function within tropical headwater streams.