The invention concerns an oxidation dyeing composition for keratinous fibres, in particular for human keratinous fibres and more particularly hair, comprising, in a medium suited for dyeing, at least an oxidation dyeing agent, and also at least an amphiphilic polymer including at least an ethylenically unsaturated monomer with a sulphonic group, in free form or partly or completely neutralised and further at least a hydrophobic part. The invention also concerns dyeing methods and devices using said composition.