In this study, the Potential theory-based Manes method was used to describe competitive multicomponent adsorption of VOC and water vapor onto activated carbon. The thermodynamically consistent method was extended to water-miscible VOCs using a Raoult's law-like relation. The method uses as input the pure single-component adsorption isotherms, which were obtained from the modified Dubinin-Radushkevich (MDR) model for VOCs and the Qi-Hay-Rood (QHR) model for water vapor. The MDR model was applicable for the studied VOCs (2-propanol, acetone, n-butanol, toluene, 1,2,4-trimethylbenzene) with an overall r(2) value of 0.998. The QHR isotherm provided a good description for water vapor adsorption on activated carbon with 0.999 r(2) value. Experimental validation tests revealed that the multicomponent adsorption isotherm model predicted the VOC adsorption capacity during competitive adsorption with water vapor with an overall mean relative absolute error (MRAE) of 1.9% for non-polar VOCs and 5.2% for polar VOCs. These results are encouraging, as they indicate a good agreement between modeled and experimental results. Hence, the model can potentially be integrated with dynamic adsorption models to optimize adsorber design and operation or model adsorption kinetics.