Process for dyeing keratin fibres in which said fibres are treated, in one or more steps, with one or more cosmetic compositions containing the following ingredients, taken together or separately in said composition(s): a) one or more dyes chosen in particular from oxidation dyes and direct dyes, of synthetic or natural origin, preferably chosen from ortho-diphenols ODPs; b) one or more titanium salts, in which the titanium in particular has the oxidation state 2, 3 or 4, preferably the oxidation state 4; optionally b1) one or more carboxylic acids of formula below: formula or a salt thereof, in which: - A represents a monovalent group when n has the value zero or a polyvalent group when n is greater than or equal to 1, saturated or unsaturated, cyclic or non-cyclic and aromatic or non-aromatic hydrocarbon-based group comprising from 1 to 50 carbon atoms which is optionally interrupted with one or more heteroatoms and/or optionally substituted, in particular with one or more hydroxyl groups; preferably, A represents a monovalent (C 1 -C 6)alkyl group or a polyvalent (C 1 -C 6)alkylene group optionally substituted with one or more hydroxyl groups; - n represents an integer between 0 and 10 inclusive; preferably, n is between 0 and 5, such as 0, 1 or 2; c) one or more anionic thickening polymers derived from the polymerization of at least one monomer bearing an organic monoacid function. a) one or more dyes chosen in particular from oxidation dyes and direct dyes, of synthetic or natural origin, preferably chosen from ortho-diphenols ODPs; b) one or more titanium salts, in which the titanium in particular has the oxidation state 2, 3 or 4, preferably the oxidation state 4; optionally b1) one or more carboxylic acids of formula below: formula or a salt thereof, in which: - A represents a monovalent group when n has the value zero or a polyvalent group when n is greater than or equal to 1, saturated or unsaturated, cyclic or non-cyclic and aromatic or non-aromatic hydrocarbon-based group comprising from 1 to 50 carbon atoms which is optionally interrupted with one or more heteroatoms and/or optionally substituted, in particular with one or more hydroxyl groups; preferably, A represents a monovalent (C 1 -C 6)alkyl group or a polyvalent (C 1 -C 6)alkylene group optionally substituted with one or more hydroxyl groups; - n represents an integer between 0 and 10 inclusive; preferably, n is between 0 and 5, such as 0, 1 or 2; - A represents a monovalent group when n has the value zero or a polyvalent group when n is greater than or equal to 1, saturated or unsaturated, cyclic or non-cyclic and aromatic or non-aromatic hydrocarbon-based group comprising from 1 to 50 carbon atoms which is optionally interrupted with one or more heteroatoms and/or optionally substituted, in particular with one or more hydroxyl groups; preferably, A represents a monovalent (C 1 -C 6)alkyl group or a polyvalent (C 1 -C 6)alkylene group optionally substituted with one or more hydroxyl groups; - n represents an integer between 0 and 10 inclusive; preferably, n is between 0 and 5, such as 0, 1 or 2; c) one or more anionic thickening polymers derived from the polymerization of at least one monomer bearing an organic monoacid function.