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Changing climate and fire regimes are profoundly affecting temperate coniferous forests, driving greatly reduced tree cover postfire. However, whether similar changes are present in the understory of these forests remains less well-understood. We sampled understory plant communities in 20 plot pairs across Greater Yellowstone (Wyoming, USA) in July and August 2021, with each including one plot burned at short (<30 year) fire-return interval and one plot burned in the same most recent fire but not burned previously for >125 years. We also included 11 plot pairs meeting our definition of short- and long-interval fire that were sampled 12 years after the 1988 Yellowstone fires in summer 2000. We also used previously collected published and unpublished data to compare understory communities following recent (2016) short-interval fires to those following the previous long-interval fire in the same general area. In each plot, percent cover of understory plant species was estimated in 0.25-m2 quadrats, and species richness determined via a whole-plot sweep. Understory plant community cover, richness, and diversity did not differ by interval class, but species able to persist in drier conditions and in lower vegetation zones became more abundant following shot interval fire. Further, previously distinct understory communities following long-interval fire in two regions of Greater Yellowstone became slightly more similar following recent short-interval fire. Dissimilarity between plot pairs increased with greater historical snowfall and decreased with time since fire and postfire winter snowfall. These changes to understory plant communities may continue with ongoing shifts in climate and fire across temperate and boreal forests.