Vapor intrusion has been recognized since the 1990s as a potential pathway of concern in contaminated sites. Vapor intrusion is the migration of volatile contaminants from the subsurface into overlying structures. Due to the presence of groundwater contamination under an old industrial site located in New Jersey, a vapor intrusion (VI) investigation was conducted at commercial and residential buildings located on and around the site to determine whether any of the volatile organic compounds have migrated to off-site into the nearby buildings. Sub-slab soil gas and indoor air samples were collected and analyzed for volatile organic compounds using the USEPA Method TO-15. The analytical data were compared against background ambient air data and New Jersey Department of Environmental Protection (NJDEP) soil gas and indoor air screening levels. The results of the study revealed that chlorinated volatile organic compound including trichloroethene (TCE), tetrachloroethene (PCE) and chloroform have migrated to the buildings adjacent to the site. Concentrations of TCE, PCE, and chloroform detected in these buildings have exceeded the NJDEP VI screening levels. An active subsurface depressurization (SSD) system was installed under the sub-slab of the impacted buildings to remediate VI intrusion. The post-mitigation sampling was conducted to determine whether the SSD system was working as intended. The results of post-mitigation sampling have confirmed that the SDS systems were working and very effective at reducing indoor air exposures at the impacted buildings. Based on the results of the study, the VI investigation was expanded to include other buildings adjacent to the site and use an appropriate technology to mitigate vapor intrusion at the affected buildings.