A process for preparing an alkoxysilane with an acidic chloride content of less than 10 ppm by weight, comprising:reacting a chlorosilane with an alcohol in a water-free and solvent-free phase to form a product mixture containing alkoxysilane and residual acidic chloride, with removal of resultant hydrogen chloride from the product mixture,then adding liquid or gaseous ammonia, in an amount corresponding to a stoichiometric excess, based on the content of acidic chloride, to form an ammonia-containing product mixture,treating the ammonia-containing product mixture at a temperature between 10 and 50.degree. C., wherein the ammonia and acidic chloride undergo neutralization, to form a crude product, and optionally, then separating off a salt formed in the course of neutralization, from the crude product, andrecovering the alkoxysilane by distilling the crude product.