Eucalypt is one of the most-planted broadleaf genera around the globe, exhibiting high yield, plasticity and growing capacity on a broad range of environments. The main objective of this study is to present the integration of a specific module for eucalypt short-rotation plantations into ECOSMOS (Ecosystem Model Simulator). Different calibrations and validations, from intensively monitored sites, experimental networks, and plots in commercial stands were performed. We calibrated all ECOSMOS model biophysical and physiological parameters for the Eucalyptus module using three micrometeorological experiments. A generic genotype was calibrated and applied to evaluate the model performance in response to contrasting environments and genotypes, on a dataset from an experimental network with high Genotype x Environment interactions. The model was applied over commercial eucalypt plantations sites, where re-calibration was necessary for four parameters of the ECOSMOS- Eucalyptus module related to leaf carbon allocation and specific leaf area, because of significant differences in genotypes and management among datasets. Results showed the consistency of the biophysical and physiological processes solved by the model, simulated energy and carbon fluxes, soil water dynamics, and growth of different plant components when compared with observations; Nash-Sutcliffe efficiency (NSE) of 0.93, 0.43 and 0.27 for net radiation, net ecosystem exchange and evapotranspiration, respectively were obtained for the validation dataset. The generic genotype calibration varied greatly in simulating the eucalypt stem growth of the 26 lo- cations. The generic calibration can be used as reference for eucalypt plantation' areas in Brazil; however, a re-calibration is recommended for operational applications to adjust the ECOSMOS-Eucalyptus module to the management conditions, management practices and genotypes used by companies.