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Extended-spectrum β-lactamases (ESBL) give rise to resistance against penicillin and cephalosporin antibiotics in multiple bacterial species. The present study was conducted to map genetic determinants and related attributes of ESBL-producing bacteria in three wild aquatic bird species and chickens at the “Trimmu Barrage” in district Jhang, Punjab province, Pakistan. To study the prevalence of ESBL-producing bacteria, a total of 280 representative samples were collected from wild bird species; cattle egrets (<i>Bubulcus ibis</i>), little egrets (<i>Egretta garzetta</i>) and common teals (<i>Anas crecca</i>) as well as from indigenous chickens (<i>Gallus gallus domesticus</i>) originating from a local wet market. The isolates were confirmed as ESBL producers using a double disc synergy test (DDST) and bacterial species were identified using API-20E and 20NE strips. A polymerase chain reaction (PCR) was used to detect ESBL genetic determinants and for genus identification via 16S rRNA gene amplification. A phenotypic antimicrobial susceptibility test was performed for ESBL-producing isolates against 12 clinically relevant antibiotics using the Kirby–Bauer disk diffusion susceptibility test. A phylogenetic tree was constructed for the sequence data obtained in this study and comparative sequence data obtained from GenBank. The overall prevalence of ESBL-producing bacteria was 34.64% (97/280). The highest percentage (44.28%; 31/70) of ESBL-producing bacteria was recovered from chickens (<i>Gallus gallus domesticus</i>), followed by little egrets (<i>Egretta garzetta</i>) (41.43%; 29/70), common teal (<i>Anas crecca</i>) (28.57%; 20/70) and cattle egrets (<i>Bubulcus ibis</i>) (24.28%; 17/70). Five different ESBL-producing bacteria were identified biochemically and confirmed via 16S rRNA gene sequencing, which included <i>Escherichia coli</i> (72; 74.23%), <i>Enterobacter cloacae</i> (11; 11.34%), <i>Klebsiella pneumoniae</i> (8; 8.25%), <i>Salmonella enterica</i> (4; 4.12%) and <i>Pseudomonas aeruginosa</i> (2; 2.06%). Based on PCR, the frequency of obtained ESBL genes in 97 isolates was <i>bla</i>_CTX-M (51.55%), <i>bla</i>_TEM (20.62%), <i>bla</i>_OXA (6.18%) and <i>bla</i>_SHV (2.06%). In addition, gene combinations <i>bla</i>_CTX-M + <i>bla</i>_TEM, <i>bla</i>_TEM + <i>bla</i>_OXA and <i>bla</i>_CTX-M + <i>bla</i>_SHV were also detected in 16.49%, 2.06% and 1.03% of isolates, respectively. The ESBL gene variation was significant (<i>p</i> = 0.02) in different bacterial species while non-significant in relation to different bird species (<i>p</i> = 0.85). Phylogenetic analysis of amino acid sequence data confirmed the existence of CTX-M-15 and TEM betalactamases. The average susceptibility of the antibiotics panel used was lowest for both <i>Klebsiella pneumoniae</i> (62.5% ± 24.42) and <i>Salmonella enterica</i> (62.5% ± 31.08) as compared to <i>Enterobacter cloacae</i> (65.90% ± 21.62), <i>Pseudomonas aeruginosa</i> (70.83% ± 33.42) and <i>Escherichia coli</i> (73.83% ± 26.19). This study provides insight into the role of aquatic wild birds as reservoirs of ESBL-producing bacteria at Trimmu Barrage, Punjab, Pakistan. Hence, active bio-surveillance and environment preservation actions are necessitated to curb antimicrobial resistance.