High quality bermudagrass (Cynodon dactylon [L.] Pers.) forage production is a vital component of Southeastern U.S. agriculture. Previous research indicates that environmental stresses like elevated CO2 may significantly affect crop productivity and weed competitiveness and ecological shifts. Although the effects of elevated CO2 on C4 plants like bermudagrass could be marginal, the growth, vigor, and herbicide tolerance of C3 weeds can be affected profoundly. In the final two years of a seven-year study investigating the effects of management practices and elevated CO2 levels on bermudagrass forage production, we aimed to evaluate how these treatments impacted weed competition and diversity. From 2018 to 2025, bermudagrass was grown in a coarse-textured soil bin at the USDA-ARS National Soil Dynamics Laboratory in Auburn, AL. Open-top chambers delivered either ambient or elevated CO2 (+ 200 mg kg-1), and plots were either managed annually with fertilizer and herbicide or left unmanaged. In the final two years, elevated CO2 had no significant effect on total biomass production (bermudagrass + weeds), but in unmanaged plots, elevated CO2 resulted in a significantly greater proportion of weeds. While some C4 grasses and sedges were observed in this experiment, most weed species were C3. Consequently, C3 species dominance was generally high, especially in managed plots exposed to elevated CO2. Weeds were observed and identified in all plots, but those managed with fertilizer and herbicide had a greater proportion of bermudagrass plants to weeds, as well as lower weed densities. Species diversity indices yielded significantly greater species richness under elevated CO2 conditions. Moreover, we observed greater weed diversity with elevated CO2, which was exacerbated without proper nutrient and weed management. This provides compelling evidence that substantial shifts in weed diversity could occur due to environmental change factors like elevated CO2 and the lack of a proper crop management program.