During August and September 2012, seven cases of West Nile neuroinvasive disease were identified in three north-eastern counties of Croatia. Four cases were reported in Osijek-Baranja County, two in Brod-Posavina County and one in Vukovar-Srijem County. The median age of the patients was 62.7 years. All patients were hospitalized for 2-5 weeks. The patients from Slavonski Brod had more severe clinical presentation of disease with prolonged hospitalization. Medical entomological research was carried out in 64 localities, where 1785 mosquitoes were captured. Among the analyzed mosquitoes, 114 were determined to be Culex pipiens and subjected to molecular characterization for the presence of virus. No viral RNA was detected in mosquitoes. Subsequent public health measures taken include mosquito control in all settlements where disease was detected.