BACKGROUND Antibacterial resistance is a growing concern worldwide, including in Mozambique. Diarrhea is an important cause of mortality in Mozambique, yet few local studies have reported on the resistance of bacterial pathogens in this context. Therefore, this study aims to characterize antibiotic susceptibility patterns of Salmonella, Shigella and Campylobacter spp. among patients with diarrhea, including those who are HIV-infected and-uninfected. METHODS We conducted antibiotic susceptibility testing on 157 stool isolates recovered from 129 patients aged between 0 and 80 years with diarrhea, including HIV infected (n = 68) and-uninfected individuals (n = 61), assisted at two health centers in Maputo city. The isolates comprised of 99 Salmonella, 45 Shigella and 13 Campylobacter strains. The Kirby-Bauer disk diffusion method was used on Mueller-Hinton II agar for Salmonella and Shigella spp., while Mueller-Hinton II agar with 5% defibrinated sheep blood was used for Campylobacter spp. We tested six antibiotics listed on the national essential medicines list, including ciprofloxacin, erythromycin, azithromycin, trimethoprim-sulfamethoxazole, gentamicin, and tetracycline. RESULTS All isolates were resistant to at least one antibiotic. A high percentage of Salmonella spp. isolates were found to be resistant to trimethoprim-sulfamethoxazole (89.9%, n = 89), erythromycin (88.9%, n = 88) and tetracycline (76.8%, n = 76). In addition, 86.6% (n = 39) and 68.9% (n = 31) of Shigella isolates were resistant to trimethoprim-sulfamethoxazole and tetracycline, respectively. The majority of Campylobacter isolates (92.3%, n = 12) were resistant to erythromycin, azithromycin and tetracycline. Multidrug resistance (MDR) was observed in 79.8% of Salmonella spp., 76.9% of Campylobacter spp., and 57.8% of Shigella spp. Drug susceptibility profiles for Salmonella spp. and Campylobacter were similar in both HIV-1 infected and uninfected patients. However, Shigella spp. isolates obtained from patients without HIV infection were significantly more likely to be resistant to erythromycin, azithromycin or to exhibit multidrug resistance than those obtained from patients with HIV-1 infection (p < 0.05). All Shigella spp. and Campylobacter spp. isolates were susceptible to gentamicin. CONCLUSIONS Our study highlights concerning rates of antibiotic resistance and MDR among diarrheal bacterial pathogens in Mozambique. Further research is needed to understand the impact of HIV, ART therapy and immunosuppression on antibiotic resistance. Urgent interventions are essential to prevent the spread of resistant strains.