Woody encroachment and its effects on terrestrial ecosystems have been well-studied. However, the effect on riparian and aquatic ecosystems, specifically denitrification, has been lacking. Riparian areas of headwater prairie streams were historically dominated by grasses, but have become increasingly covered by woody vegetation. To determine potential consequences of woody plant invasion on denitrification, three adjacent reaches were delineated from two branches of King’s Creek, which drains Konza Prairie Biological Station. The three reaches are comprised of different riparian vegetation: grassy, woody, and woody vegetation removed. Potential and actual denitrification were measured along longitudinal transects away from the stream in each reach. Riparian denitrification was an order of magnitude higher earlier in the growing season (p<0.0001). The grassy riparian buffers tended to have lower rates of denitrification than both the forested and removal reach. Denitrification did not show a strong relationship with distance to the stream. Potential denitrification was measured for stream substrata. Root wads and mosses had 4x higher potential denitrification than other substrata. These results suggest that woody plant invasion may be increasing riparian denitrification and changing the dominant stream denitrification substrata from grass roots to mosses. Increasing riparian denitrification may also be off-set by altered vegetative uptake.