Kosewko [kɔˈsɛfkɔ] is a village in the administrative district of Gmina Pomiechówek, within Nowy Dwór County, Masovian Voivodeship, in east-central Poland. It lies approximately 6 kilometres (4 mi) north of Nowy Dwór Mazowiecki and 36 km (22 mi) north-west of Warsaw.