The study of bioelectrochemical systems (BESs) is gaining importance due to their versatility and wide applications, contributing to a circular bioeconomy. Electrochemically active microorganisms (EAMs) are crucial for catalyzing BES reactions and efficient operation. Applying poised potential in BESs has demonstrated the enrichment of EAMs and improved BES performance. However, in contaminated environments, it remains unclear whether the chemistry of the environment overshadows electrochemical selection. Chlorate is a toxic compound that restricts microbial community composition in BES. The aim of this study was to investigate the dynamic of electrochemical selection of electroactive chlorate-resistant microorganisms in a BES inoculated with sediment from northern Chile. For this purpose, sediment samples were enriched in a three-electrode cell through chronoamperometry with a poised potential of-0.55 V (vs. Ag/AgCl) for 112 days. Electrochemical activity was measured with cyclic voltammetry (CV), and bacterial growth was confirmed using scanning electron microscopy (SEM). Microbial diversity was analyzed via Next Generation Sequencing, and chlorate-resistance EAMs were isolated from the community obtained and characterized. The results showed the enrichment of EAMs that achieved a maximum cathodic current density of 21 mu A/cm2. CV confirmed electrochemical activity, and microbial community analysis and scanning electron microscopy showed that attached and planktonic communities changed progressively throughout the experiment. From the communities, three new chlorate-resistant and electroactive isolates were obtained. Thus, this study demonstrated the feasibility of enriching EAMs from chlorate-pressured environments and paved the way for expanding electrochemical selection as a strategy for electro-bioaugmentation and bioremediation.