This dataset contains the multiphysics model developed in COMSOL Multiphysics 6.2 to study carboplatin effects on tumor growth and the tumor microenvironment in triple-negative breast cancer (TNBC). The model integrates tumor cell proliferation, drug transport (PK/PD), DNA–platinum adduct formation, oxygen transport, and growth-induced solid stress. The dataset includes the COMSOL model file (.mph), parameter values, and model setup details required to reproduce the results reported in the associated manuscript.