Quantitative analyses of calcareous nannofossils were carried out on 102 Middle Miocene samples from the scientific borehole at Baden-Sooss (Vienna Basin). All the samples can be assigned to nannoplankton Zone NN5. The content of Helicosphaera walbersdorfensis allows correlation with the Mediterranean nannoplankton Subzone MNN5a. Typical near-shore forms such as small reticulofenestrids followed by Umbilicosphaera jafarii, Reticulofenestra haqii, Coccolithus pelagicus and Reticulofenestra pseudoumbilica dominate the calcareous nannoplankton assemblages. Inter-species correlations and correlations to stable isotopes and magnetic susceptibility together with multivariate statistical methods (Cluster analysis, Indicator value method, nonmetric Multidimensional Scaling) enabled the reconstruction of trends in the paleoenvironment of the upper water mass during this part of the Badenian. Low variations in abundance of ecologically sensitive species suggest relatively low fluctuating environments. The deeper part of the core (40 to 102 m) shows opposite oscillating trends (with long periods) in salinity and temperature. Around 70 m of the core the salinity maximum is combined with a temperature minimum, while a salinity minimum and temperature maximum can be found around 50 m. Trends in the upper core part are more discontinuous, possibly due to gaps in the sedimentation record caused by intensified tectonics. Generally, a linear trend towards slightly increasing salinity, eutrophication and lowered temperatures could be documented for the upper core part.