Process for preparing isocyanate-based or isothiocyanate-based microcapsules, which comprises the following steps: (a) providing an internal non-aqueous phase, comprising at least one isocyanate having two or more isocyanate groups or at least one isothiocyanate having two or more isothiocyanate groups, and comprising a hydrophobic active ingredient to be encapsulated having an aldehyde, carboxylic acid or ester functionality; (b) providing an external aqueous phase, comprising at least one protective colloid and a catalyst, wherein the protective colloid is selected from the group consisting of diols, in particular ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, isomeric butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-octanediol, 1,2-decanediol, 1,2-dodecanediol, and polyols, in particular triols, in particular glycerol and ethoxylation and propoxylation products thereof, trimethylolpropane and ethoxylation and propoxylation products thereof, polyvinyl alcohol (PVOH) and derivatives thereof, in particular ammonium- or sulfonate-functionalized polyvinyl alcohols, polyphenols, in particular 1,3,5-trihydroxybenzene, starch or chemically, mechanically and/or enzymatically modified starch, carboxymethylcellulose and polyvinylpyrrolidone, and mixtures of the aforementioned compounds; (c) mixing the internal non-aqueous phase and the external aqueous phase, optionally in the presence of a stabilizer and/or an emulsifier, to obtain an oil-in-water emulsion; (d) first crosslinking by adding an amine that reacts at an acidic pH; (e) further crosslinking by adding an amine that reacts at an alkaline pH, so as to obtain microcapsules; (f) curing the microcapsules obtained in step (e); and optionally: (g) separating the microcapsules from the reaction solution and, if necessary, drying the microcapsules. (a) providing an internal non-aqueous phase, comprising at least one isocyanate having two or more isocyanate groups or at least one isothiocyanate having two or more isothiocyanate groups, and comprising a hydrophobic active ingredient to be encapsulated having an aldehyde, carboxylic acid or ester functionality; (b) providing an external aqueous phase, comprising at least one protective colloid and a catalyst, wherein the protective colloid is selected from the group consisting of diols, in particular ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, isomeric butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-octanediol, 1,2-decanediol, 1,2-dodecanediol, and polyols, in particular triols, in particular glycerol and ethoxylation and propoxylation products thereof, trimethylolpropane and ethoxylation and propoxylation products thereof, polyvinyl alcohol (PVOH) and derivatives thereof, in particular ammonium- or sulfonate-functionalized polyvinyl alcohols, polyphenols, in particular 1,3,5-trihydroxybenzene, starch or chemically, mechanically and/or enzymatically modified starch, carboxymethylcellulose and polyvinylpyrrolidone, and mixtures of the aforementioned compounds; (c) mixing the internal non-aqueous phase and the external aqueous phase, optionally in the presence of a stabilizer and/or an emulsifier, to obtain an oil-in-water emulsion; (d) first crosslinking by adding an amine that reacts at an acidic pH; (e) further crosslinking by adding an amine that reacts at an alkaline pH, so as to obtain microcapsules; (f) curing the microcapsules obtained in step (e); and <EOS>