A method for manufacturing dialkylzinc and dialkylaluminum monohalide that makes it possible to efficiently manufacture both dialkylzinc and dialkylaluminum monohalide of high purity and at a high yield on an industrial scale with a single reaction from zinc halide and trialkylaluminum as raw materials, while suppressing the production of precipitants in the reaction process and suppressing the adhesion of precipitates to the equipment and the admixture thereof into the product. The method for manufacturing dialkylzinc and dialkylaluminum monohalide by reacting zinc halide with trialkylaluminum, includes using trialkylaluminum with a hydride concentration of 0.01% by mass to 0.10% by mass, and separating dialkylzinc essentially not containing aluminum from reactants and then separating dialkylaluminum monohalide essentially not containing zinc.