Updated publication reference for PubMed record(s): 34908431. The aim of this study was to develop a suitable method to preserve fecal samples for metaproteomics analyses when flash-freezing is not an option. Fecal samples were collected from conventional adult C57BL/6 mice and combined into a fecal master mix. The fecal master mix was then split into 48 subsamples that were subjected to different preservation treatments. The following six preservation methods were tested: flash-freezing in liquid nitrogen followed by storage at -80°C, immersion in RNAlater® and storage at room temperature, immersion in RNAlater® and immediate storage at -80°C, immersion in 95% ethanol and storage at room temperature, immersion in a RNAlater-like buffer “NAP buffer” and storage at room temperature, and immersion in an autoclaved RNAlater-like buffer “Autoclaved NAP buffer” and storage at room temperature. Proteins were extracted from the samples after being stored for 1 and 4 weeks. There were 4 replicates per treatment and time-point. Samples were analyzed by LC-MS/MS and the data were analyzed with Proteome Discoverer against a large database of mouse microbiota protein sequences.