The invention concerns compounds derived from diaminopyrazole of formula (I), wherein: R₁ is a linear or branched radical selected among C₂, C₃, C₄ aminoalkyl radicals or C₂, C₃, C₄ aminoalkenyl radicals, or one of the physiologically acceptable salts thereof. The invention also concerns compositions containing said compound for dyeing keratinous fibers and the method using said compositions. ##STR1##