Objective We aimed to systematically review the impact of local estrogen use in combination with a pessary on vaginal complications in postmenopausal women with pelvic organ prolapse (POP). Methods We searched databases including Medline, Embase, PubMed, Clinical Trials and the Cochrane Central Register of Controlled Trials for relevant literature published in English from inception to 31 May 2021. Only randomized controlled trials (RCTs) and cohort studies were included. Results In total, five studies were included (three RCTs, one prospective study and one retrospective cohort study). The meta-analysis was performed with subgroups. Our results indicated a significantly lower incidence of bacterial vaginosis (BV) among postmenopausal women who used estrogen than among controls, with a total pooled odds ratio (OR) of 0.29 (95% confidence interval [CI]: 0.11-0.72; I-2 = 38%; p = 0.008). The summary ORs of the estrogen use group were 0.98 (95% CI: 0.59-1.63; I-2 = 41%; p = 0.95) for vaginal ulceration, 0.80 (95% CI: 0.42-1.54; I-2 = 29%; p = 0.50) for vaginal bleeding and 0.74 (95% CI: 0.35-1.58; I-2 = 35%; p = 0.44) for vaginal discharge. Conclusions Local estrogen in combination with a pessary could decrease the BV rate among postmenopausal women with POP. However, consensus regarding the value of estrogen use for decreasing other pessary complications has not yet been reached. Additional multicenter RCTs with large sample sizes should be conducted to better understand the effect of estrogen use on reducing pessary-related complications.