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According to National Resources Inventory data, Kentucky bluegrass is now present in over 85% of the areas sampled in the northern Great Plains of the USA. This non-native, perennial, cool season grass has the potential to develop a dense thatch layer and root mat near the soil surface affecting how water infiltrates and runs off of a site. We used rainfall simulators and the water droplet infiltration time test to determine whether the presence of a Kentucky bluegrass root mat, thatch, and litter layers affected water infiltration and therefore hydrologic function of these Kentucky bluegrass dominated ecosystems. Rainfall simulation results show time to runoff is primarily controlled by rainfall intensity. As intensity increased from 63.5 mm/hr to 127 mm/hr, time to runoff was shortened. Hydrophobicity test results show that when dry, Kentucky bluegrass litter is very hydrophobic and is significantly more hydrophobic than thatch, root mat or mineral soils. However, hydrophobicity of bluegrass litter is significantly reduced after it has been wetted. Results also show how strata with the highest percent of organic matter (dead Kentucky bluegrass blades) were also the most hydrophobic. Results highlight the need for further research on Kentucky bluegrass effects on infiltration and runoff and the importance of management strategies that minimize excessive accumulation of Kentucky bluegrass litter.�