The present invention relates to a composition for dyeing keratin fibers, comprising: at least one nonionic ether of a polyoxyalkylenated fatty alcohol of formula (i) R—(O-Alk)nOR′ (i), in which: —R denotes a linear or branched, saturated or unsaturated C10-C30 hydrocarbon-based radical, —R′ denotes a linear or branched, saturated or unsaturated C10-C30 hydrocarbon-based radical, which may be substituted with a hydroxyl radical, —n is an integer between 1 and 100 inclusive, and —Alk represents a linear or branched, preferably linear, (C1-C6)alkylene group such as ethylene or propylene, preferably ethylene, —at least one fatty alcohol comprising at least 20 carbon atoms —at least one chemical oxidizing agent. The present invention also relates to a process using this composition, and to a multi-compartment device that is suitable for implementing the invention.
