Introduction. Increasing microbial resistance to conventional pharmaceuticals calls for nonpharmaceutical treatments of vaginitis. This systematic review summarizes the efficacy of the antiseptic agent boric acid (BA) as a treatment option for microbial vaginitis in comparison to conventional therapies and proposes clinical recommendations. Materials and Methods. PubMed and Embase were searched for “boric acid” and “microbial vaginitis.” A protocol was registered on PROSPERO (CRD42020160146). Inclusion criteria included clinical trials, observational and interventional studies, including case series/reports. Exclusion criteria included in vitro and animal studies, non-English language, and no BA treatment outcome. Primary outcomes included microbial, clinical, and complete cure. Secondary outcomes included adverse events, relapse/reinfection rates, evidence levels, microorganisms, treatment regimens, and follow-up time. Data were extracted to a predefined Excel sheet. Results. Of 195 identified unique articles, 54 were retrieved and 41 met our inclusion criteria. Heterogeneity precluded the conduction of a meta-analysis. Conclusion. An average cure rate of 76% was found for vulvovaginal candidiasis BA treatment. Recurrent bacterial vaginosis was controlled with BA and 5-nitroimidazole with promising results. Maintenance BA was equal to maintenance oral itraconazole therapy in vulvovaginal candidiasis and bacterial vaginosis in a retrospective study. Prolonged BA monotherapy cured three of six recurrent Trichomonas infections. Adverse events (7.3%) were typically mild and temporary. Based on our findings and the rising antimicrobial therapy resistance, we suggest intravaginal BA 600 mg/day for 2 weeks for (recurrent) vulvovaginal candidiasis and 600 mg/day for 2-3 weeks for recurrent bacterial vaginosis. Rare resistant Trichomonas infections can be treated with BA 600 mg × 2/day for months and in combination with oral antimicrobials. We suggest a maintenance regimen of BA 600 mg × 2/week for recurrent vulvovaginal candidiasis. In case of resistant bacterial vaginosis, we suggest BA 600 mg × 2-3/week. Data on maintenance therapy and BA treatment of bacterial vaginosis and trichomoniasis are however limited.