Groundwater contamination is a major threat to people depending on groundwater for their daily water supply. The quality of groundwater has degraded due to the release of toxic contaminants in groundwater from natural as well as man-made practices, thus resulting in the spread of water-related diseases to humans. Thus, this study was planned to assess the groundwater contaminants and their associated health effects on the residents of Lahore City, Pakistan. To assess the physicochemical properties of groundwater, randomly, 62 samples of groundwater were collected from all over the study area. The data showed that the Electrical Conductivity (EC), Total Dissolved Solids (TDS), pH, and sulfates exceeded the safe limit of the National Environmental Quality Standards (NEQS), and the concentration of heavy metals (lead, chromium, and cadmium) was also much higher than the NEQS and World Health Organization (WHO) recommended levels. The multivariate analysis, such as Principal Component Analysis (PCA) and cluster analysis, confirmed that toxic heavy metals, including lead, chromium, and cadmium, originated from similar sources, such as industrial activities in the study area. The results from chronic daily intake, hazard quotient, and cancer risk also demonstrated that lead, chromium, and cadmium tested heavy metals showed potential carcinogenic and non-carcinogenic risks to children and adults in the study area. Thus, this study concluded that groundwater is highly contaminated and not fit for human consumption. Future studies are required for constant monitoring of groundwater quality and to develop mitigation methods to improve its quality on urgent basis.