Conservation of biodiversity recently has focused on the importance of pollinator services for the preservation of threatened plant species in fragmented landscapes such as the tallgrass prairie biome. In this study, we assessed the influence of local and landscape floral resource diversity and abundance on bumble bee (Bombus Latreille) diversity and abundance at eight tallgrass prairie sites in Iowa. We calculated a landscape floral resource index (LRI) for areas within 500- and 700-m radii of each site based on the density and diversity of flowering plant species in polygons of different landscape elements. LRI values, areas of each landscape habitat type, and the diversity and abundance of bumble bee–used flowering ramets at each site were compared with bumble bee diversity and abundance at the site. Bumble bee diversity was best predicted by a model including the LRI of grasslands surrounding sites at 500 m, which explained most of the variance, and the abundance of bumble bee–visited plants at the site. Bumble bee abundance was best predicted by a model including the percent of the landscape in grasslands at the 700-m radius, which explained most of the variance, and the abundance of bumble bee–visited plants at the site. Our results reveal that bumble bee diversity at tallgrass prairie patches is influenced by the availability of resources in the landscape, particularly in grasslands, and to a lesser extent by site characteristics, indicating the importance of spatial scale for creating successful pollinator management plans in fragmented landscapes.