Soil moisture is a key variable in off-road mobility. Mobility analysis was conducted based on three soil moisture sources: WindSat (a satellite), LIS (a computer model), and in situ ground sensors (assumed to represent ground truth). Mobility of six vehicles, each with different ranges of sensitivity to soil moisture, was examined in three test sites. Two methods were used: a simplified method based on time series and a fulleatured terrain method. The results demonstrated that the effect of the soil moisture error on mobility predictions is complex and may produce very significant errors in mobility analysis for certain combinations of vehicles, seasons, and climates. Soil moisture biases vary in both direction and magnitude with season and location. Furthermore, vehicles are sensitive to different ranges of soil moistures. In the wet season, differences in soil strength resulted in more significant differences in mobility predictions than in the dry season.