A new rhodium‐catalyzed synthetic method is described for the preparation of 1,3‐thiaphospholes. Cyclization reactions of various 1,2,3‐thiadiazoles with phosphaalkynes in the presence of a rhodium precursor and a dcypp ligand afford the corresponding 1,3‐thiaphospholes via denitrogenation of the 1,2,3‐thiadiazoles.