Currently, analysis of treated wastewater discharged from the wastewater treatment plants (WWTP) inflowing into recipients involves determination of concentrations of organic substances (chemical and biological oxygen demand) and nutrients (nitrogen and phosphorus). In this study, the impact of effluent on organismic bioindicators and degree of resistance of bacterial isolates to antimicrobial drugs originating from wastewater has been evaluated with the aim to determine toxic effects on aquatic (fish, Carassius gibelio) and terrestrial (earthworm, Eisenia fetida, Oligochaeta) organisms, and indirectly on human health. The ecotoxicological testings on bioindicator model organisms were conducted, measuring mechanisms of multixenobiotic resistance and parameters of oxidative stress. Cytogenetic damages were determined by micronucleus test, and mutagenic effects with Ames test. Comparative microbiological analyses were made with conventional methods and mass spectrometry analyser. Results of this study show that treated wastewater (leaving WWTP) changed environmental parameters by introduction of xenobiotics, contributed to microbial contamination and antimicrobial resistance, histopathological tissue changes and oxidative stress of examined organisms. Hencewith, our approach encompassed an integrated overview of the impact of treated wastewater on key environmental and organismal parameters.