The present work aims to assess the origin of the boron contamination of groundwater that affect some areas of central-Adriatic Italy, through the use of boron and strontium isotopic analysis. The research results indicate that boron contamination is mainly related with salinization of groundwater attributable to the uprising of connate groundwater and mixing processes between more shallow fresh groundwater and deeper saline groundwater. As a result, the main boron contamination of groundwater is not related to anthropogenic inputs but rather to natural processes.