Alkyl or alkenyl N,N-dimethylchalcogenocarbamates were easily prepared by a stepwise treatment of bis(N,N-dimethylcarbamoyl) dichalcogenides with NaH or NaBH4, followed by various alkylating agents or acetylenes bearing electron-withdrawing substituents. The one-step conversion of alkyl or alkenyl N,N-dimethylselenocarbamates or N,N-dimethyltellurocarbamates into the corresponding symmetrical dialkyl or dialkenyl dichalcogenides was also achieved efficiently by treating with SnCl4.