AbstractCyclic voltammetry (CV) is expected to cause changes in the biocathode composition, especially when using low scan rates. A recent finding stated that CV triggered further biocatalytic activity in microbial electrosynthesis systems (MES), leading to the aim of our study: to investigate the invasiveness of CV on MES. The present study confirms that a CO2 elongation MES biocathode composition changes during and right after the CV. Oxidation peaks differ over repeated CV‐cycles while metal compounds and biomass were released in the biocatholyte. After CV, the current increased temporarily for up to 20 days and the metal compounds decreased from the biocatholyte solution. Further, the sole short application of open cell voltage was shown to shortly increase the current. Evidently CV affects the studied biocathode, which complicates the use of CV as an analysis technique in MESs. However, the positive effect CV has on biocathode current density may provide methods to boost reactor performance and maintain productivity.