The remediation of groundwater which contains chlorinated organic compounds (COCs) by nanoscale bimetallic catalysts has received increasing interest in recent years. This report presents the dechlorination of 2,4-dichlorophenol (2,4-DCP) by Pd-Fe bimetallic nanoparticles in the presence of humic acid (HA) to investigate the feasibility of using Pd-Fe for the in situ remediation of contaminated groundwater. Our experimental results indicated that HA had an adverse effect on the dechlorination of 2,4-DCP by Pd-Fe nanoparticles. The rate constant kvalues of 2,4-DCP dechlorination were 0.017, 0.013, 0.009, 0.006 and 0.004 min-1 for HA concentrations of 0, 5, 10, 15 and 20 mg/L, respectively. The relationship between HA dosage and k values can be described as a linear model.