This paper investigates the thermal conductivity of cemented backfill. Two major measurement methods, namely, steady state and unsteady state, are compared. Effect of backfill design parameters such as pulp density and binder content, along with sample homogeneity and sample size, are studied. Thermal conductivity of backfill with and without sodium silicate additive, as a new binder, is investigated. A novel method for interpreting thermal conductivity of backfill is presented by introducing backfill as amultiphase porous material for which the effects of physical parameters, such as degree of saturation, porosity, and thermal conductivity of solid particles, are studied. The results of this research help to better understand the thermal interaction of backfill with the surrounding rock mass and therefore contribute to progressive improvement of backfill technology.