Background: Tribe Proteeae consisting of Proteus, Providencia, and Morganella species are critical opportunistic pathogens causing various health care-associated infections. Widespread extended-spectrum β-lactamase (ESBL) activities have been reported among members of these groups of organisms. Aim: This study aimed to detect ESBL genes in clinical isolates of these bacteria from Nnamdi Azikiwe University Teaching Hospital (NAUTH). Materials and Methods: Two hundred and sixteen Gram-negative bacilli isolated from patients receiving care in NAUTH were identified using the Microbact 12A Gram-negative bacilli identification system. Antimicrobial susceptibility tests were performed on the isolates using antibiotics of various classes. The isolates resistant to any third-generation cephalosporins were screened for ESBL activity using the combination disc test. The presence of cefotaximase (CTX), oxacillinases (OXA), and transmission electron microscopy (TEM) genes were determined using polymerase chain reaction. Results: Out of the 216 Gram-negative isolates, 12 (5.6%) were Proteus spp., 3 (1.4%) were Morganella spp., and 8 (3.7%) were Providencia spp. The prevalence of the Proteeae bacteria was 23/216 (10.6%). Of the 23 Proteeae bacteria, 5 (21.7%) were confirmed phenotypically as ESBL producers, while 3 (13%) expressed the actual ESBL genes. CTX, OXA, and TEM genes were detected in all three isolates. Furthermore, 13% of the isolates exhibited carbapenem resistance. Conclusion: The results confirmed that ESBL-producing Proteeae bacteria existed in NAUTH. The incidental detection of carbapenem resistance among the Proteeae isolates whispers terror in waiting because carbapenems are last-resort antibiotics for managing life-threatening ESBL infections. This worrisome development highlights the need to improve infection control practices in Nigerian tertiary hospitals drastically.