Geothermal reservoirs, oil wells, radioactive waste disposals, and deep underground mines deal with high-temperature and high-pressure problems. The thermo-hydromechanical coupling may significantly affect the behavior of the rock mass in these applications. Fractures and joints are the main conduits of thermal and hydraulic transition. The displacement discontinuity method (DDM) is ideally suited to model problems containing fractures. However, the DDM in its original formulation is restricted to elasticity problems. It is formulated in this study to take into account the thermo-hydromechanical effects. A numerical formulation and implementation for the thermo-hydromechanical DDM is derived. The proposed numerical model is validated in three parts. The poroelastic, thermoelastic, and thermo-hydromechanical couplings are each validated by analytical or experimental results. The results showed good agreement between the proposed numerical model and analytical or experimental results over various periods. The validations proved the accuracy and applicability of the proposed thermo-hydromechanical numerical model in a wide range of problems. Furthermore, the thermo-hydromechanical effect on crack opening displacement (COD) is modeled. Numerical simulation showed that the maximum COD due to only thermal effects may be reached after almost a year. (C) 2020 Elsevier Ltd. All rights reserved.