The simulation model of seasonal dynamics of 137Cs in the components of the oak forest ecosystem EcoradOak_CS_FW has been further developed, which now includes first- and second-order consumers. The radiocesium redistribution is modeled in a full-scale food web of a forest ecosystem of the soil–vegetation–herbivores–predator type. The algorithm used in the model allows us to take into account the effects of the soil, meteorological, phenological, and physiological factors on the behavior of radionuclide in the food web and predict radiological situations under various conditions of radioactive fallout. Data obtained with the model on the contamination of animals with radiocesium are used to calculate the dynamics of the internal dose. The results of modeling can be used in the rationing of forest products of deciduous forests. The model is also applicable to the study of potassium redistribution in the trophic chain of a deciduous forest ecosystem.