Direct access to trideuteriomethoxylated aromatic and heteroaromatic compounds has been developed. Various aryl and heteroarylhalides underwent d3-methoxylation under mild reaction conditions by using a catalyst system composed of the commercially available monodentate phosphane ligand tBuXPhos and Pd(OAc)2. Inexpensive CD3OD served as an efficient trideuteriomethoxylating agent.