Abstract Background: Moraxella catarrhalis is an opportunistic gram-negative diplococcus that primarily infects the respiratory tract, in patients living with HIV particularly those with low CD4 counts, it can act as a serious pathogen causing issues like pneumonia, sinusitis, and bronchitis, rarely it can spread to cause bacteremia or meningitis in highly immunocompromised individuals. The organism is also associated with resistance to penicillins¹,². Objective: This study determined the occurrence of M. catarrhalis among HIV patients attending a HAART clinic in a tertiary hospital in Edo State, Nigeria, and evaluated the antibiotic susceptibility pattern of the isolates. Methods: This descriptive laboratory-based study examined 100 HIV-positive patients. N swab specimens were collected aseptically and cultured on blood agar, chocolate agar, and MacConkey agar. Presumptive isolates were identified by colony morphology, Gram staining, oxidase, and catalase tests. Antimicrobial susceptibility testing was performed by the Kirby-Bauer disk diffusion method, and beta-lactamase production was assessed using the rapid acidometric filter paper method. Results: M. catarrhalis was isolated from 24 of 100 samples, giving an overall prevalence of 24.0%. Isolation was highest among patients with CD4 counts below 200 cells/µL. The isolates were most susceptible to sparfloxacin, ciprofloxacin, amoxicillin-clavulanic acid, ofloxacin, and chloramphenicol. All isolates were resistant to penicillin and produced beta-lactamase. Conclusion: M. catarrhalis was recovered from HIV patients in this setting, with complete resistance to penicillin and intermediate susceptibility to several non-beta-lactam agents. In immunocompromised patients, especially those with advanced HIV disease, susceptibility testing should guide therapy.