Summary: We prove existence of a weak solution to the Navier-Stokes-Fourier system on a bounded Lipschitz domain in \(\mathbb{R}^3\). The key tool is the existence theory for weak solutions developed by Feireisl for the case of bounded smooth domains. We prove our result by inserting an additional limit passage where smooth domains approximate the Lipschitz one. Results on sensitivity of solutions with respect to the convergence of spatial domains are shortly discussed at the end of the paper.