Introduction: antibiotic-associated diarrhea (AAD) is a frequent complication of antibiotic therapy in hospitalized or institutionalized older adults and may progress to Clostridioides difficile infection. Objective: to assess whether probiotics, compared with placebo or standard care, reduce AAD incidence in this population. Methods: a systematic review with meta-analysis, following PRISMA, searched Embase, PubMed/MEDLINE, CINAHL, Cochrane CENTRAL and LILACS through 23 August 2026, including randomized, non-randomized and cohort studies; risk of bias was assessed with RoB2/ROBINS-I and certainty of evidence with GRADE. Results: of 3,060 records, 16 studies (17 reports) were included. The pooled risk ratio (RR) for AAD incidence was 0.98 (95%CI, 0.79-1.22), with no significant difference; for C. difficile diarrhea, RR was 0.51 (95%CI, 0.29-0.88), with low-certainty evidence. Conclusion: probiotics did not significantly reduce AAD in hospitalized or institutionalized older adults, although C. difficile diarrhea was reduced; findings do not support routine use in this population.