BACKGROUND: Seasonal influenza vaccine (SIV) uptake in the United States remains suboptimal, requiring new and innovative strategies. OBJECTIVE: To evaluate the impact of a behavioral peer comparison (PC) intervention on SIV uptake in community pharmacies across the United States. METHODS: A cluster randomized study was conducted across a national network of Walmart community pharmacies (> 4500 sites) during the 2019-2020 influenza season. The clusters consisted of 416 markets, each containing an average of 11 pharmacies. All pharmacies in a market were randomly assigned to either no intervention or the PC intervention, a software-delivered communication informing on-site staff, including pharmacists and pharmacy technicians, of their pharmacy's weekly performance, measured as SIV doses administered, compared with that of peer pharmacies within their market. The outcome was the pharmacy-level cumulative SIV doses administered during the intervention period (September 1, 2019,-February 29, 2020). Linear regression models were used to estimate the PC impact, with multiway cluster-robust SEs estimated by market and state. RESULTS: A total of 4589 pharmacies were enrolled in the study, with 2297 (50.1%) randomized to the control group and 2292 (49.9%) randomized to the PC intervention group. Overall, compared with the control pharmacies, the PC pharmacies administered 3.7% (95% CI -0.3% to 7.9%) additional SIV doses. Among large-format pharmacies, the PC pharmacies administered 4.1% (95% CI 0.1%-8.3%) additional SIV doses compared with the controls. Historically low-performing large-format PC pharmacies administered 6.1% (95% CI 0.5%-11.9%) additional SIV doses compared with the controls. No statistically significant treatment effects were observed among small-format pharmacies. CONCLUSION: Our findings demonstrate that PCs can improve SIV uptake among large-format community pharmacies, with historically low-performing pharmacies potentially exhibiting the greatest relative impact. Wide-scale implementation of PCs in community pharmacies may help to further improve SIV uptake in these settings.