Coinage metals (Au, Cu and Ag) are state-of-the-art electrocatalysts for the CO2 reduction reaction (CO2RR). Size-dependent CO2RR activity of Au and Cu has been studied, and increased H2 evolution reaction (HER) activity is expected for small catalyst particles with high population of undercoordinated corner sites. A similar consensus is still lacking for Ag catalysts because the ligands and stabilizers typically used to control particle synthesis can block specific active sites and mask inherent structure-property trends. This knowledge gap is problematic because increased performance and catalyst utilization are still needed to improve economic viability. We combined density functional theory, microkinetic modeling, and experiment to demonstrate a strong size-dependence for pristine Ag particles in the sub-10 nm range. Small diameter particles with a high population of Ag edge sites were predicted to favor HER, whereas CO2RR selectivity increased towards that of bulk Ag for larger diameter particles as the population of Ag(100) surface sites grew. Experimental results validated these predictions and we identified an optimal particle diameter of 8-10 nm that balanced selectivity and activity. Particles below this diameter suffered from poor selectivity, while larger particles demonstrated bulk-like activity and reduced catalyst utilization. These results demonstrate the size-dependent CO2RR activity of pristine Ag catalysts and will help guide future development efforts.