Technical Abstract: Fires in mountain big sagebrush (Artemisia tridentata spp. vaseyana (Rydb.) Beetle) plant communities historically shifted dominance from woody to herbaceous vegetation. However, fire return intervals have lengthened with European settlement and sagebrush dominance has increased at the expense of herbaceous vegetation in some sagebrush plant communities. Management actions may be needed in dense sagebrush stands to decrease sagebrush to increase herbaceous vegetation. Prescribed fire is often used to treat dense sagebrush stands; however, mechanical treatments, such as mowing, are becoming increasingly used because they are more controllable and do not pose an inherent risk of escape compared to fire. However, information on the effects of burning and mowing treatments on herbaceous vegetation and if fire and mowing applications elicited similar vegetation responses is limited. We evaluated responses to prescribed fire and mowing for three years post-treatment in mountain big sagebrush plant communities. The burned and mowed treatments generally increased herbaceous cover, density, and production compared to the untreated controls (P < 0.05). However, neither treatment educed a response in perennial forbs (P > 0.05). Vegetation generally responded similarly to burned and mowed treatments; however, the burned treatment had less sagebrush, greater herbaceous vegetation production, and more bare ground than the mowed treatment (P < 0.05). These differences should be consideration when selecting treatments to reduce sagebrush.