Hybrid Napier grass, Pennisetum "Pakchong 1" has been considered as a potential species to use for wastewater treatment. However, variation of NO3-:NH4+ ratios in various types of wastewater and change of NO3-:NH4+ ratios during the treatment process could affect to the plants and also the eficiency of the wastewater treatment systems. This study aim to assess the effects of NO3-:NH4+ ratios on growth, morphology, nitrogen(N) uptake, and mineral allocation of hybrid Napier grass. The plants were grown on a standard nutrient solution (Smart & Barko, 1985) with different NO3-:NH4+ ratios (%) (100:0, 75:25, 50:50, 25:75, and 0:100) at the same concentration (500 µM N). All treatments were incubated in the greenhouse for 70 days. The highest shoot elongation rate and average leaf area were found in the treatment of 25:75 NO3-:NH4+. However, the N ratios did not affect relative growth rates, N uptake,or chlorophyll concentrations. The concentration of Ca in plant tissue was signiicantly reduced when the plants were supplied with high NH4 +:NO3 - ratios. Based on the results, the hybrid Napier grass can grow well with any ratios of NO3-:NH4+. It could therefore be a good candidate for treating wastewater with variable N sources.