2-(Alkoxymethyl)acrolein of the formula ##STR1## is produced from acrolein, an alcohol ROH and formaldehyde, in one step, with a good yield being obtained. The acrolein is reacted with a substantially equimolar quantity of a source of formaldehyde in the presence of at least an equimolar quantity of the alcohol ROH and a catalytic quantity of a catalyst system based on a secondary amine and a mineral acid at a pH value of the reaction mixture in the range of 1 to less than 7.
