The present invention relates to a process for the oxidation dyeing of keratin fibers implementing: a) a step of pretreating said fibers by application to said fibers of a cosmetic composition (B) comprising: i) at least one fatty substance in an amount of greater than or equal to 10% by weight relative to the total weight of the composition (B)； and ii) at least one metal catalyst； b) optionally a washing, rinsing, drying and/or rubbing-dry step； c) followed by a step of dyeing by application to said fibers of a cosmetic composition (A) comprising: i) at least one oxidation base, preferably chosen from para-phenylenediamines, bis(phenyl)alkylenediamines, para-aminophenols, ortho-aminophenols, heterocyclic bases preferably comprising at least two nitrogen atoms, and addition salts thereof； ii) optionally at least one coupler； and iii) at least one chemical oxidizing agent. The dyeing process makes it possible to significantly improve the dyeing properties of the coloration, in particular in terms of selectivity, of chromaticity, and of color intensity and uptake. The use of a composition which is rich in fatty substances, i.e. greater than 10%, and contains at least one catalyst pretreatment, before oxidation dyeing, allows a clear improvement in the dyeing properties, in particular in terms of dye uptake onto keratin fibers, of strength and of chromaticity and of selectivity of the color.
