Chlorinated ethenes are of environmental concern with most reports of successful microbial-mediated remediation being associated with major dechlorinating groups such as Dehalococcoides (Dhc) species. However, limited information is available on the community dynamics and dechlorinating activities of indigenous non-Dhc groups. Here, we present evidence of dechlorination of tetrachloroethene (perchloroethylene, PCE) in groundwater samples by indigenous microbial communities. 100 % PCE conversion to ethene was observed in acetate-stimulated 24 week-microcosms (controls; 15 %). Microbial community profiles showed dominance by groups such as Proteobacteria, Spirochaetes, Firmicutes, Methanomicrobiaceae and Methanosarcinaceae. Pareto-Lorenz (PL) analyses suggested an adapted (45 % PL value) but variable bacterial community (55.5 % Δt(week)) compared to Archaea (25 % PL value; 46.9 % Δt(week)). Our findings provide evidence of dechlorinating potential of indigenous microorganisms and useful information on their dynamics which may be exploited for in situ groundwater bioremediation.