Hospital wastewaters are highly complex effluents acting as a hotspot for antibiotic resistant bacteria. Especially, Gram-negative bacteria bearing multiple antibiotic resistant genes are increasingly found in hospital wastewaters. The aim of this study was to evaluate the presence of extended spectrum beta-lactamases (ESBL) and carbapenemase producing Enterobacteriaceae in hospital wastewaters from one Slovenian and two Austrian hospitals, as well as the occurrence of antibiotic resistant genes encoding for VIM, KPC, NDM, CTXM and OXA beta-lactamases in isolates from hospital wastewater. The results indicated high levels of ESBL producing Enterobacteriaceae in ranges up to 107 cfu/mL. Carbapenemase producing Enterobacteriaceae and OXA 48-type CPE were present in ranges up to 105 cfu/mL. Out of 89 multiplied polymerase chain reaction (PCR) amplicons, only 36 were positive for different β-lactamase gene families, among those only three isolates were identified as multiresistant. The dominant ESBL family was CTXM in 19 different isolates. This was followed by 10 OXA-48 positive isolates and 10 VIM positive isolates. KPC or NDM carbapenemases were not identified with PCR screening of the isolates. Hospital wastewaters serve as a reservoir for nearly all clinically important antibiotic resistances. The importance of evaluating such potential environmental reservoirs is especially evident when outbreak cases could not be linked to an epidemiological source.