The alien freshwater shrimp Palaemon sinensis was recently confirmed in freshwater areas of Japan. To clarify the potential introduction vector of P. sinensis, the occurrence of this shrimp was researched in fishing bait shops in Japan. The shrimp was sold in bait shops in Tokyo, Yokohama, Shizuoka, Nagoya, Osaka, Hiroshima and Fukuoka under the product name “Shirasa ebi”. Five fishes, Pseudorasbora parva, Micropercops swinhonis, Rhinogobius brunneus, Tridentiger brevispinis, and Macropodus ocellatus, one crustacea, Tachea chinensis, and one aquatic insect, Hesperocorixa cf. distanti were unintentionally contained in shrimp samples. P. sinensis was also confirmed in lentic water environments such as main streams and side pool of rivers and agricultural waterways located in Kanagawa, Hyogo, Okayama, Shimane, Fukuoka and Saga prefectures.