Objectives: Multidrug resistance (MDR) and emergence of extended-spectrum β-lactamases (ESBLs) among uropathogenic Escherichia coli have been reported worldwide, but there was no information on the detection of blaCTX-M-15 in major teaching hospitals in Libya. The aim of the study was to investigate the occurrence of CTX-M-15 β-lactamases producers isolated from five teaching hospitals in Tripoli, Libya. Methods: A total of 346 urine samples were collected from hospitalized patients in five teaching hospitals with a diagnosis of urinary tract infection (UTI). Phenotypic confirmation of ESBLs was confirmed by E-test strip; all ESBL-producing E. coli isolates were screened for the blaCTX-M-15 gene. Results: The distribution of ESBL-producing E. coli varied among the five hospitals. The highest proportion was identified in Tripoli Medical Centre (67.6%). There were extremely high proportions of isolates resistant to ceftriaxone, cefepime, and ceftazidime (93.0–100.0%) among ESBL producers compared to non-ESBL producers (2.2–4.7%). MDR was detected in 22.2% of isolates. The majority of isolates (85.9%) in which blaCTX-M-15 was identified were ESBL producers. There was a correlation (p < 0.001) between expression of CTX-M-15 and resistance to ceftazidime. Conclusions: The isolation of MDR ESBL-producing uropathogens expressing the CTX-M-15 gene will limit the choices clinicians have to treat their patients with UTIs. Continued surveillance and implementation of efficient infection control measures are required.