Time-lapse methodology was applied to cross-hole electrical resistivity tomography (CHERT) to investigate two groundwater contamination sites. In the first case study, resistivity profiles were used to delineate the transport direction and spatial distribution of the contaminant, which can serve as a basis for adjusting the remediation treatment by the remediation team. In the second case study, changes in electrical conductivity were used to evaluate the remediation reagent’s transport direction and area of effect, and this was used to indirectly verify the effectiveness of the remediation efforts. CHERT equipment was installed simultaneously at the monitoring wells, which enhanced the benefits of the boreholes, enabling them to be even more economical. In large-scale groundwater contamination sites or sites with complex hydrogeological environments, application of CHERT techniques can result in greater amounts of data, particularly in analyzing localized preferential flow paths. This data would be greatly beneficial to the remediation of groundwater contamination sites and long-term groundwater management.