Batch experiments were performed to study the effect of coexisting compounds on trichloroethylene (TCE) dechlorination and sorption in the presence of iron. Competitive sorption of TCE was observed with naphthalene as a coexisting contaminant, but the TCE reduction rate slightly increased with naphthalene, which is hardly subject to reduction. With carbon tetrachloride, nitrate, and chromate as reducible cocontaminants, the competitive reduction of TCE was observed in binary-contaminant systems. The reduction rate constant of TCE by iron filings decreased 1.5 times with carbon tetrachloride because of the competition for electrons. The TCE reduction rate with nitrate decreased five times because of the competition for electrons and the enhanced passivation. The sorbed mass of TCE on iron surface with chromate increased more than that without chromate because of the formation of (Cr, Fe)(OH)3 precipitations.