The Badenian marine littoral Grund Formation at Grund in the Molasse Zone of Lower Austria provided marine and terrestrial faunas in the same strata. They allowed correlation between continental and marine biozonations of the European Middle Miocene. In the present paper for the first time the included fossil remains of Ruminantia are described in detail. Six isolated teeth and nine postcranial skeletal elements are determined as Ruminantia indet., Pecora indet., cf. Micromeryx flourensianus Lartet, 1851, Micromeryx cf. styriacus Thenius, 1950, and cf. Eotragus clavatus (Gervais, 1850). The biochronological age indicated by cf. M. flourensianus, M. cf. styriacus and cf. E. clavatus is restricted to the European mammal zones late MN5 to MN6. Consequently the hitherto identified age of late MN5 for these sediments is confirmed by the occurrence of the Ruminantia represented. The taxonomic composition further indicates paleoecological conditions compatible with earlier reconstructions of the environment as either islands or the elevated parts of a peninsula or rising terrain of the hinterland. In any of these settings groundwater levels would have been low and the vegetation a covering of woods, bushes and shrubs. Comparisons with Austrian ruminant faunas of the early MN5/late Karpatian (Oberganserndorf and Teiritzberg) support the interpretation of a change during MN5 towards a drier climate under more or less stable temperatures in Central Europe.