The present invention relates to a composition for washing and conditioning keratin materials, comprising, in a physiologically acceptable medium: a) one or more anionic surfactants, b) one or more surfactants chosen from nonionic surfactants, and amphoteric or zwitterionic surfactants, and c) one or more solid branched fatty alcohols containing more than 25 carbon atoms. The invention also relates to the use of the said composition for washing and conditioning keratin materials, and to a process for washing and conditioning keratin materials using it.