A fully coupled Thermal - Mechanical - Biological (TMB) model was developed in COMSOL Multiphysics to simulate temperatures and settlement observed at a Municipal Solid Waste (MSW) landfill in Ste. Sophie, Quebec. The thermal model included heat transfer and storage, aerobic and anaerobic heat generation (biological model), heat conduction at the base and heat flux due at the top due to to net radiation and convection. The mechanical model was based on a viscoelastic Kelvin-Voight model. A temperature-dependent biodegration-induced settlement term was added to the mechanical model to simulate waste settlement. A unique modelling approach was developed that allowed optimization of model parameters over a single simulation which included both filling and post-filling stages. The optimized model was able to simulate temperatures and settlement field data reasonably well. Modelling results and sensitivity analysis illustrate the need for a coupled TMB model to simulate temperature-dependent, biodegradation-induced settlement of MSW in landfills.