The water resource is highly demanded in the Yangtze River Delta with a developed economy. Long-term exploitation has posed threats of artificial pollution and seawater intrusion to the shallow groundwater. This study aimed to reveal the hydrochemical characteristics and health risks of shallow groundwater in the coastal plain of the Yangtze River Delta. Also, possible factors affecting groundwater quality were discussed. Methods, such as typical hydrochemical tests, water quality assessment and health risk models, were applied to achieve the study targets. The results showed that the shallow groundwater was slightly alkaline, and the average values of total dissolved solids (TDS) and total hardness (TH) were 930.74 mg/L and 436.20 mg/L, respectively. The main hydrochemical types of groundwater were Ca+Mg–HCO₃ and Ca/Na–HCO₃, accounting for 44.3% and 47.5%, respectively. In addition, As concentration was generally high, with a mean value of 0.0115 mg/L. The principal factors affecting the groundwater components include water-rock interactions (especially silicate), cation exchange, seawater intrusion and human activities. As in the groundwater is strongly influenced by the redox of Fe, Mn, and NO₃^-. The results of the groundwater quality evaluation indicated that the shallow groundwater in some regions was unsuitable for drinking and agricultural irrigation. Health risk assessment showed that 44.3% of the water samples had significant health risks, which was attributed to the high As concentration. Therefore, it is urgent to establish long-term As monitoring to maintain sustainable groundwater management and drinking water safety. The results of this study can provide essential data for water resource management and human health protection in the Yangtze River Delta.