In Brandenburg, northeastern Germany, an outbreak of zoonotic Dirofilaria repens in a sledge dog kennel was detected in January, 2012. Using the modified Knott test, 8 out of 28 adult dogs were microfilaria positive. A D. repens-specific PCR based on the internal transcribed spacer 2 region detected filarial DNA in 11 of these dogs. Northeastern Germany is currently considered to be free of Dirofilaria. The 39% prevalence within the kennel and the fact that the dogs transiently stayed in endemic areas only during the winter suggest that autochthonous infections occurred. Analysis of weather data shows that extrinsic development of Dirofilaria was continuously possible in the summers of 1994-2012, thus allowing active transmission within the area.