The remobilization of carbon reserves from stems to storage organs plays a key role in determining final rice yield. Often ignoring or providing an oversimplified description of such process within simulation models potentially undermines their reliability under a variety of conditions, given that remobilization is non-linearly regulated by irrigation and fertilization rates. However, knowledge on this topic is much more advanced compared with available formalizations in several crop models. The modeling approach proposed here gives an interpretation of the contribution of carbohydrate redistribution during rice grain filling based on a reanalysis of published information. The model was designed targeting a degree of adherence to physiological processes coherent with the current state-of-the-art of crop models. The result is a set of equations driven by few parameters reflecting crop physiological traits, whose calibration allowed to give reliable estimates of NSC remobilization in Indica and Japonica cultivars. The new model is currently included in the WARM model (Confalonieri et al., 2009), but can be easily integrated in other rice simulators based on the concept of net photosynthesis or simulating the gross assimilation of CO2 and respiration losses. The explicit description of NSC in different plant organs would allow to refine the simulation of their mutual source–sink relationships. Currently our remobilization model does not account for such complex interactions, and considers NSC in stems as a source pool exploited during grain filling. Further, our model would benefit from a finer integration of senescence and remobilization processes and from a process-based description of the influence of soil water and plant nitrogen availability.