The data contains epilithic biofilm, water chemistry, and catchment data for 28 streams in Greenland. 14 streams in Zackenberg (74°28'N, 20°34'W), between the 20th of August and 3rd of September 2017, six streams in Qeqertarsuaq (69°15'N, 53°31'W), between the 18th and 25th of September 2018, and eight streams in Narsaq (60°55'N, 46°52W), between the 4th and 6th of August 2022. We collected biofilm samples for measuring algal and total biomass, measured community composition in-situ using a bbe BenthoTorch, collected water samples for measuring water chemistry, and determined catchment parameters using GIS-based tools. Biofilm characteristics (i.e. chlorophyll-a, ash-free dry weight, and community composition), water chemistry (i.e. ammonium, phosphate, nitrate, and silica), and catchment characteristics (i.e. NDVI, area, and slope) was measured for all streams. Biofilm and water chemistry samples were collected and analysed using standard methods, and catchment characteristics were determined using GIS resources. The data was collected in order to study relationships between epilithic biofilm characteristics and water chemistry and catchment properties