Crossline resistivity tomography was developed to find out anomalous seepage pathways in an embankment dam. By applying crossline tomography to the investigation of embankment dams, leakage pathways can be effectively located because the crossline tomogram presents resistivity distribution in the horizontal plane of an embankment dam. To test the effectiveness of crossline tomography, we applied it to data from an experiment designed to delineate anomalous seepage pathways in the embankment dam. The method yields relatively accurate geoelectric structure of the dam when applied to synthetic data. In the crossline resistivity tomogram, abrupt discontinuities of a low resistivity band corresponding to the core of the dam can be interpreted as leakage pathways. Application to real data obtained from an embankment dam in Korea yields the result which accurately depicts two anomalous seepage pathways. The identified pathways were consistent with low resistivity zones in the dipole-dipole resistivity section obtained on the crest of the dam. One pathway was confirmed by visual inspection of the dam, and afterward, by trenching.