Nitroaromatic compounds, such as 2,4,6-trinitrotoluene (TNT), are common munition-derived pollutants encountered at facilities used in the manufacturing, processing, and disposing of explosives. The environmental fate of TNT and other organic contaminants in soils is largely determined by its interaction with soil clay minerals and organic matter. Previous research has shown that humic acid can potentially impact the sorption of pesticides, such as dichlorbenil, to clay minerals. These studies show that humic acid had no impact on pesticide sorption by K⁺-saturated clays, but could either enhance or suppress sorption by Ca²⁺-saturated clays. However, it is not well known how the interaction between clay minerals and organic substances could facilitate the sorption of TNT. The objective of this study was to determine the effect humic substances have on the interaction between TNT and clay minerals. In this study, sorption and desorption of TNT by K⁺-saturated and Ca²⁺-saturated smectite, kaolinite, and hectorite along with the respective humic acid-clay complexes were examined using batch-equilibration and x-ray diffraction (XRD). The sorption of TNT on K⁺-saturated and Ca²⁺-saturated smectite was significant and reached equilibrium within 2 h, whereas limited sorption was observed for kaolinite. The effect of humic acid on TNT sorption/desorption kinetics and capacity on these minerals will be discussed.