Arctic tundra wetlands support abundant waterbirds, but invertebrate prey communities may change with climate warming. Increased influx of nutrients and labile dissolved organic matter (DOM) from thawing permafrost may alter the relative importance of organic matter (OM) sources, with associated changes in relative biomass of taxa dependent on different sources. In six wetland types, we used stable isotopes (δ13C, δ15N) to compare contributions of four OM sources (periphytic microalgae, cyanobacteria, macrophytes, and peat) to the diets of nine macroinvertebrate taxa. Relative OM contributions within invertebrate taxa were similar among wetland types. Cyanobacteria comprised only 2–7% of OM sources for all taxa in shallow wetland types (<1 m), but up to 25% for oligochaetes and Physidae in deeper wetlands. Macrophytes were minor OM sources (<13%) in all wetland types except deep open lakes (21–26%). Peat typically comprised 20–40% of OM sources except for Physidae (mostly 50–80%). Microalgae were the dominant OM source for most taxa (47–78%, mean ⁓60%), although less for Oligochaeta and much less for Physidae (9–32%). High periphyton production with very depleted δ13C values likely results from continuous daylight illuminating shallow depths, high N and P levels, and very high pCO2 derived from bacterial respiration of DOM leached from thawing permafrost. Invertebrate consumption of microalgae and peat appears often to involve bacterial intermediates. Impacts of warming on invertebrate prey availability will likely depend not on shifts in OM sources, but on changes in overall area or number of shallow ponds.