The present invention relates to a process for preparing monomethylhydrazine by methylating hydrazine or hydrazinium hydrochloride or hydrazinium dihydrochloride with methyl chloride and/or a methano/HCl mixture, characterized in that the reaction mixture formed in the methylation is reacted with an organic base from the group of the alkylamines or alkanolamines and monomethylhydrazine is removed by distillation from the reaction mixture in a low boiler fraction and the low boiler fraction is optionally subjected to a further distillation.