Chlorinated aliphatic hydrocarbons and monoaromatic hydrocarbons are major soil and water pollutants as a result of their widespread anthropogenic use. Soil contamination is of particular concern as it results in offsite contamination of groundwater and surface waters by migration of contaminants through and with soil materials. Co-contamination of soil with chlorinated aliphatic hydrocarbons and monoaromatic hydrocarbons allows for the application of aerobic bioremediation to achieve the simultaneous mineralization of both types of compounds. Bench scale laboratory experiments were run to select and enrich indigenous microbial isolates capable of cometabolizing two representative chlorinated aliphatic hydrocarbons, cis-1.2-dichloroethylene (cis-DCE) and trichloroethylene (TCE), mixed with benzene, toluene, ethylbenzene, and three isomers of xylene (BTEX) provided as substrates. The well-characterized toluene-oxidizing bacteria, Pseudomonas plecoglossicida, as well as 7 unidentified strains of bacteria isolated from potentially contaminated soil and sludge samples, were examined for their ability to degrade mixtures of BTEX, TCE or cis-DCE in liquid culture. This process was used as an initial screen to select the best bacterial isolate for further investigation. Based on results of these experiments, Pseudomonas plecoglossicida, showing higher mineralization extent of the mixure, especially TCE and cis-DCE, was chosen to investigate further. The aerobic simultaneous bioremoval of the mixture of TCE, cis-DCE, and BTEX was studied under different conditions through laboratory-scale batch experiments in 6-day incubation. Studies were performed on selected parameters (soil physicochemical properties—pH, temperature, and moisture; nutrient concentrations—nitrogen and phosphorus; contaminant properties—contaminant iii iv concentration, ratio of growth substrate (BTEX) to nongrowth substrate (chloroethenes); microbial inoculation amount) and optimization carried out to improve TCE/cis-DCE/BTEX mixture removal. The central composite design (CCD) together with the response surface methodology (RSM) was applied to evaluate the interactive effects of the parameters, as well as the optimal bioremoval conditions. The bioremoval of the mixture varied, depending on the conditions, and interactions among these compounds, especially growth and nongrowth substrate, were complicated. The presence of toluene, nonetheless, enhanced the bioremediation of other compounds unanimously. Overall, the methods and technologies presented here can be good candidates for bioremediation of the mixed wastes-contaminated sites.