The novel process for preparing dialkyl dicarbonates by reacting the corresponding alkyl haloformates with alkali metal hydroxides, alkaline earth metal hydroxides and/or carbonates in the presence of water-immiscible organic solvents and in the presence of a catalyst is characterized in that the catalyst used is at least one tertiary alkylamine of the formula (I)NR1R2R3, (I)where the substituents are each as defined in the description.