Soil salinity has become a major stress factor that reduces crop productivity worldwide. Sodium (Na) toxicity in a number of crop plants is tightly linked with shoot Na overaccumulation, thus Na exclusion from shoot is crucial for salt tolerance in crops. In this study, we identified a member of the high-affinity K transport family (HAK), OsHAK12, which mediates shoots Na exclusion in response to salt stress in rice. The mutants showed sensitivity to salt toxicity and accumulated more Na in the xylem sap, leading to excessive Na in the shoots and less Na in the roots. Unlike typical HAK family transporters that transport K, OsHAK12 is a Na-permeable plasma membrane transporter. In addition, was strongly expressed in the root vascular tissues and induced by salt stress. These findings indicate that OsHAK12 mediates Na exclusion from shoot, possibly by retrieving Na from xylem vessel thereby reducing Na content in the shoots. These findings provide a unique function of a rice HAK family member and provide a potential target gene for improving salt tolerance of rice.