The first-order Raman spectrum of K[2]S was measured over the temperature range from 10 to 742 K. The temperature dependence of the linewidth can be explained using results from the anharmonic lattice dynamics approach. Both the cubic and the quartic anharmonic interactions are of importance for this system. At 293 K, the Raman line is at ω[T2g]=128 cm[−1] with a full width at half maximum Γ[T2g]=2.9 cm[−1].