Valerianella radiata (L.) Dufr., which is native to North America, was newly found in Gyeonggi-do and Gyeongsangnam-do, Korea. This species can be distinguished from other Valerianella species in Korea by its white flowers, and the fertile fruit locule lacks a corky mass on the abaxial surface. V. radiata grows on slopes and roadsides, suggesting that it is likely to have been introduced when green sites were installed and during road construction. Its introduction into Japan has been reported, but the associated ecological risk is unknown. Here, we provide a detailed morphological description, taxonomic key to related taxa, voucher specimens, photographs, and distribution maps of its habitat.