An approach for the efficient synthesis of halogenated hydrazines via acid-mediated electrophilic hydrazinative halogenation of alkenes is disclosed. This transformation proceeds with readily available diethyl azodicarboxylate as a hydrazine source and low-cost potassium halides as nucleophilic halogen sources. A series of iodinated, brominated, and chlorinated hydrazines are facilely produced with a wide range of functional groups. The obtained products are good platform molecules. They can be conveniently converted into a variety of valuable phenelzine analogues which are appealing for development of novel drugs treating depression.