This meta-analysis aims to combine the latest research evidence to assess the effect of probiotics on preventing antibiotic-associated diarrhea (AAD) in adults. PubMed, Cochrane Library, EMBASE, and Web of Science were searched for randomized placebo-controlled trials on probiotics preventing AAD. A random or fixed effect model was used to combine the incidence of AAD (primary outcome) and the adverse event rates. The authors performed subgroup analyses to explore the effects of different participants population, probiotics species, and dosage. Thirty-six studies were included with 9312 participants. Probiotics reduced the incidence of AAD by 38% (pooled relative risk, 0.62; 95% confidence interval, 0.51-0.74). The protective effect of probiotics was still significant when grouped by reasons for antibiotics treatment, probiotic duration, probiotic dosage, and time from antibiotic to probiotic. However, there were no statistically significant increased adverse events in the probiotics group (relative risk, 1.00; 95% confidence interval, 0.87-1.14). This updated meta-analysis suggested that using probiotics as early as possible during antibiotic therapy has a positive and safe effect on preventing AAD in adults. Further studies should focus on the optimal dosage and duration of probiotics to develop a specific recommendation. Copyright © 2020 The Author(s). Published by Wolters Kluwer Health, Inc.