Background The effectiveness of patient decision aids (PtDAs) and other shared decision-making (SDM) interventions for socially disadvantaged populations has not been well studied. Purpose To assess whether PtDAs and other SDM interventions improve outcomes or decrease health inequalities among socially disadvantaged populations and determine the critical features of successful interventions. Data Sources MEDLINE, CINAHL, Cochrane, PsycINFO, and Web of Science from inception to October 2019. Cochrane systematic reviews on PtDAs. Study Selection Randomized controlled trials of PtDAs and SDM interventions that included socially disadvantaged populations. Data Extraction Independent double data extraction using a standardized form and the Template for Intervention Description and Replication checklist. Data Synthesis Twenty-five PtDA and 13 other SDM intervention trials met our inclusion criteria. Compared with usual care, PtDAs improved knowledge (mean difference = 13.91, 95% confidence interval [CI] 9.01, 18.82 [I² = 96%]) and patient-clinician communication (relative risk = 1.62, 95% CI 1.42, 1.84 [I² = 0%]). PtDAs reduced decisional conflict (mean difference = −9.59; 95% CI −18.94, −0.24 [I² = 84%]) and the proportion undecided (relative risk = 0.39; 95% CI 0.28, 0.53 [I² = 75%]). PtDAs did not affect anxiety (standardized mean difference = 0.02, 95% CI −0.22, 0.26 [I² = 70%]). Only 1 trial looked at clinical outcomes (hemoglobin A1C). Five of the 12 PtDA studies that compared outcomes by disadvantaged standing found that outcomes improved more for socially disadvantaged participants. No evidence indicated which intervention characteristics were most effective. Results were similar for SDM intervention trials. Limitations Sixteen PtDA studies had an overall unclear risk of bias. Heterogeneity was high for most outcomes. Most studies only had short-term follow-up. Conclusions PtDAs led to better outcomes among socially disadvantaged populations but did not reduce health inequalities. We could not determine which intervention features were most effective. [Box: see text]