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Storm surge has the potential to significantly increase suspended sediment flux to microtidal marshes. However, the overall effects of storm surge on microtidal marsh deposition have not been well quantified, with most modeling studies focusing on regular (astronomical) tidal flooding. Here we applied the Delft3D model to a microtidal bay‐marsh complex in Hog Bay, Virginia to quantify the contributions of storm surge to marsh deposition. We validated the model using spatially distributed hydrodynamic and suspended sediment data collected from the site and ran model simulations under different storm surge conditions with/without storm‐driven water level changes. Our results show that episodic storm surge events occurred 5% of the time at our study site, but contributed 40% of marsh deposition during 2009–2020. Our simulations illustrate that while wind‐driven waves control sediment resuspension on tidal flats, marsh deposition during storms was largely determined by tidal inundation associated with storm‐driven water levels. A moderate storm surge event can double sediment flux to most marshes around the bay and deliver more sediment to the marsh interior compared to simulations that include wind waves but not storm surge variations in water levels. Simulations of bay and marsh response to different storm surge events with varying magnitude of storm surge intensity reveal that total marsh deposition around the bay increased linearly with storm surge intensity, suggesting that future changes to storm magnitude and/or frequency would have significant implications for sediment supply to marshes at our study site. Plain Language Summary: Storm surge is a rise of water level beyond normal tidal levels caused by a storm. It can result in longer and deeper inundation on the marsh platform and potentially provide more sediment for microtidal marshes (tidal range <2 m) to gain elevation at a rate comparable to sea level rise. However, the overall importance of storm surge to sediment deposition on these marshes is not well understood. Here we used a well‐tested coastal model in a shallow microtidal bay fringed by intertidal salt marshes to run model simulations for different storm surge events with varying magnitude of storm surge intensity to determine the contributions of storm surge to marsh deposition. Our simulation results show that infrequently occurring storm surge events contributed ∼40% of marsh deposition at our study site and that total mass of marsh deposition around the bay increased linearly with the magnitude of storm surge events. Our findings have significant implications for predicting marsh change, especially if we experience a stormier future climate. Modeling studies that do not resolve storm surge effects on marsh deposition will likely underestimate rates of marsh elevation change. Key Points: A numerical model was used to quantify the contributions of storm surge on marsh deposition in a microtidal bay‐marsh complexStorm surge events occurred 5% of the time, but contributed 40% of marsh deposition during 2009–2020Marshes will likely be supplied with more sediment during storms if storm magnitudes and/or frequencies increase in the future [ABSTRACT FROM AUTHOR]