The subject of the present invention is a process for the oxidation dyeing of keratin fibers, in particular human keratin fibers such as the hair, implementing: a) a step of treating said fibers by application to said fibers of a cosmetic composition (A) comprising: i) at least one fatty substance in an amount of greater than 10% by weight relative to the total weight of the composition (A), at least one metal catalyst； ii) at least one coupler； iii) optionally at least one oxidation base, preferably chosen from para-phenylenediamines, bis(phenyl)alkylenediamines, para-aminophenols, ortho-aminophenols, heterocyclic bases, addition salts thereof and solvates thereof； b) optionally a washing, rinsing, drying and/or rubbing-dry step； c) a step of treatment by application to said fibers of an oxidizing cosmetic composition (B) comprising at least one chemical oxidizing agent； and it being understood that steps a), b) and c) can be carried out successively a), then b), then c), or else a) then c), followed by b). 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, as a 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.
