Background In this systematic review, the authors aim to assess the effect of silver diamine fluoride (SDF) in preventing and arresting caries in exposed root surfaces of adults. Types of Studies Reviewed Two reviewers independently searched for controlled clinical trials with at least 12 months of follow-up, without language or date of publication restraints, in 8 electronic databases, 5 registries of ongoing trials, and reference lists of narrative reviews. Results The authors found 2,356 unique records and included 3 trials in which the investigators randomly assigned 895 older adults. Investigators in all studies compared SDF with placebo; investigators in 1 also compared 38% SDF with chlorhexidine and sodium fluoride varnishes. The primary effect measures were the weighted mean differences (WMDs) in decayed or filled root surfaces (DFRS) and the mean differences in arrested carious lesions between SDF and control groups. The studies had low risk of bias in most domains. SDF applications had a significantly better preventive effect in comparison with placebo (WMD DFRS: 24 months, −0.56; 95% confidence interval, −0.77 to −0.36; 30 months or more, −0.80; 95% confidence interval, −1.19 to −0.42), and they were as effective as either chlorhexidine or sodium fluoride varnish in preventing new root carious lesions. SDF also provided a significantly higher caries arrest effect than did placebo (pooled results not calculated). Complaints about black staining of the carious lesions by SDF were rare among older adults. Conclusions and Practical Implications Yearly 38% SDF applications to exposed root surfaces of older adults are a simple, inexpensive, and effective way of preventing caries initiation and progression.