Abstract Silicene has recently been revisited as a 2D material with potential thermoelectric applications. Here, the thermal properties of supported silicene are determined by optothermal Raman spectroscopy. Single and multilayer silicene is grown either directly on silver (Ag) substrates or on an intermediate tin (Sn) monolayer, introduced to reduce the influence of the substrate on the physical properties of silicene. Experimental values of an effective cross‐plane thermal conductivity of 0.5 W/mK are obtained for silicene on Ag and 0.3 W/mK for silicene on stanene‐Ag. The values of the interfacial thermal conductance, on the other hand, are 0.3 and 0.5 GW/m 2 K, respectively. Heterostack engineering is confirmed as a versatile strategy for extracting relevant physical parameters in silicene and for modulating the thermal response in the 2D limit.