While creep behavior in clay rocks has been extensively studied, experimental research on Boom Clay under coupled THM conditions remains limited. To address this gap, this chapter presents a systematic experimental investigation into the THM-coupled creep behavior of Boom Clay. A series of hydro-mechanical (HM) and THM triaxial creep tests were conducted on original Boom Clay samples. The test results indicate that elevated temperature significantly accelerates creep deformation and alters its characteristic stages, highlighting the critical role of thermal coupling in long-term stability. Microstructural analyses, conducted in parallel, reveal underlying mechanisms such as particle rearrangement and pore fluid redistribution induced by thermal effects. The findings provide essential experimental data and mechanistic insights for evaluating the long-term performance and safety of geological repositories for high-level radioactive waste.