Long-term settlement of MSW landfills is a complex process, which is explained by the following two mechanisms: (1) the mechanical long-term compression of degradable organic solids (DOS) and un-degradable organic solids (UDOS); and (2) the decomposition-based compression of the DOS. Based on these two distinct settlement mechanisms, in this study, the authors propose a new estimation model to predict the long-term settlement of a MSW landfill. An optimization process using a real-coded genetic algorithm (GA) is performed to evaluate the parameters of the proposed estimation model, based on the settlement data measured at the Mountain View Landfill located near San Jose, California, USA. In comparison with the existing settlement models, the model predicts settlement very close to the measured data and closely conformed to the Grisolia and Napoleoniâ€™s long-term settlement curve. Unlike the existing models, it is the only model that can produce estimation for both long-term and short-term settlement reliably and consistently.