A new locality of the Chinese clam Sinanodonta woodiana (Lea, 1834) was found in a temporarily drained Czesławicki Pond (10.8 ha) near the village of Janisławice (Dolina Baryczy Landscape Park, Sośnie community, Ostrów Wielkopolski district, Wielkopolska region) in September 2006. In this fishpond a dense population of the Chinese clam was observed whose number was estimated as about few hundred individuals. During the second control (January 2007), we observed a few hundred clams in the same pond and we found smaller populations in adjacent ponds of the same Janisławice complex. During a detailed control of the ponds (drained in the autumn 2006) of the fishpond complex near Konradów (120 ha, 2 km SW of the Janisławice complex), only one damaged, empty shell of the Chinese clam was found. Specimens with maximum shell dimensions – 185 mm length and 140 mm width – were found in the Czesławicki Pond. Before, S. woodiana was found in Poland only in heated waters which were thought to be necessary for the development of this species. This is the first Polish record of the species in a reservoir with a natural thermal regime.