The results of studies that address thermal aspects of the subseabed disposal of high-level radioactive waste are summarized. A mathematical model is proposed for the description of thermal transport from a discrete source of heat in a fluid-saturated seabed sediment. For model parameters typical of those associated with subseabed disposal, it is demonstrated that thermally induced convection is relatively weak, and consequently, the thermal field is established primarily by conduction. However, the weak convective motion is of importance to the transport of radionuclides that may inadvertently be released into the sediment. Numerical predictions of thermal effects are presented for a reference emplacement geometry. The validity of the modeling approach was verified experimentally in a laboratory scale simulation. An initial deployment of a large-scale thermal experiment during an oceanographic expedition provided in-situ measurements of sediment thermal conductivity, which is an important parameter in the modeling. Based on the collective results of our studies, a clearer understanding of the thermal aspects of subseabed waste disposal has emerged.