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The temperature dependence of the thermal conductivity of plasma-spray-deposited monolithic coatings, as well as multilayer coatings that consisted of Al 2 O 3 and ZrO 2 that was stabilized by 8% Y 2 O 3 (YSZ), was investigated. The coatings exhibited a large reduction in thermal conductivity at all temperatures, when compared to the bulk monolithic Al 2 O 3 and YSZ. This reduction was due to porosity as well as thermal resistance that was caused by interfaces in the coatings. The largest decrease in the thermal conductivity of the coatings, relative to monolithic fully dense materials, was due to splat interfaces within each layer, as well as the coating/substrate interface. On the other hand, the multilayer coatings showed little variation in the thermal conductivity, relative to the number of layers, which suggests that the influence of interlayer interfaces on heat transfer is relatively small. A one-dimensional analysis of steady-state heat transfer has been presented to illustrate the significance of porosity, splat interfaces, and interlayer interfaces, with respect to the overall thermal conductivity of multilayer coatings.