The globally-threatened Aquatic Warbler (Acrocephalus paludicola) breeds in Europe and spends the northern winter in sub-Saharan West Africa. We attached 30 geolocators to breeding birds in the central Ukraine in 2010. Three geolocators which collected data from the autumn migration were recovered in 2011. They revealed a previously-unknown migration route via southern Europe to stopover sites in south-western France and Spain. In West Africa, one bird spent some time well south of known non-breeding areas. For the conservation of some Aquatic Warbler populations, protection of hitherto unknown stopover sites in southern Europe and Africa may be crucial.