Abstract. Moisture sorption isotherms of milled switchgrass (Panicum virgatum) were developed to provide guidelines for proper storage and drying of biomass. Samples were stored for a minimum of 8 days inside incubators set at 15°C, 25°C, or 35°C at different relative humidities, ranging from 16% to 88%. Equilibrium moisture content (EMC) data were fitted with the Henderson model and modified versions of the Chung-Pfost, Guggenheim-Anderson-deBoer (GAB), Halsey, Henderson, and Oswin models. The modified GAB model (R 2 = 0.99; SE = 0.58% d.b.) followed by the modified Henderson model (R 2 = 0.99; SE = 0.68% d.b.) produced randomized residuals and the best fit for milled switchgrass. The results have practical applications in the handling, drying, storage, and transportation of switchgrass to ensure that quality deterioration and spoilage by microorganisms are minimized.