The continuous emergence of new strains of extended-spectrum beta-lactamase (ESBL)-producing and carbapenem-resistant Enterobacteriaceae (CRE) poses a significant public health challenge. However, limited information is available on the prevalence and features of non-clinical isolates and, in particular, for isolates from the general community and non-human sources. Here, we characterized four ESBL-producing and four carbapenem-resistant (CR) Escherichia coli (EC), three ESBL-producing and one CR Klebsiella pneumoniae (KP), and two CR K. variicola (KV) species obtained from wastewater-based surveillance undertaken in Sydney from 2017 to 2019. The isolates were found to be resistant to a range of antibiotics that were critically important for human health. Genomic sequencing and phylogenetic analysis showed that EC isolates from wastewater were related to high-risk human-associated pandemic clones (ST131, ST167, ST410) and emerging human and non-human-associated clones (ST1702, ST9586). KP and KV isolates were related to globally disseminated and emerging human-associated clones (ST13, ST268), and some were detected for the first time in Australia (ST101, ST353, ST2791). Various known resistance mechanisms against β-lactams, aminoglycosides, fluoroquinolones and trimethoprim and sulfamethoxazole were found in the isolates, however, the genomic analysis also indicated novel resistance mechanisms against nitrofurantoin in EC isolates and piperacillin/tazobactam and ticarcillin/clavulanic acid in Klebsiella isolates. The virulence gene content indicated that some EC and Klebsiella isolates were likely associated with infections, while the asymptomatic carriage was suggested for other isolates. These results demonstrate a clear potential for wastewater-based surveillance to monitor resistance beyond clinical settings, which can complement hospital-based surveillance to inform infection control and prevention strategies to effectively track and control the emergence and spread of resistant pathogens.