Herein, we present the first, one-step, direct synthesis of unsymmetric phosphorotrithioates through a process involving sequential coupling of 1,1-dichloro-N,N-diethylphosphanamine with thiols and sulfenyl chloride. This method showcases excellent functional group tolerance, substrate compatibility, and mild reaction conditions, offering a streamlined approach for the challenging phosphorotrithioate synthesis. Additionally, the applicability of this method can be extended to the synthesis of mixed phosphoroselenodithioates.