The invention relates to a cosmetic composition comprising: -from 2% to 20% by weight, relative to the total weight of the composition, of one or more fatty-chain alkoxysilanes of formula (I) below: R1Si(OR2)3 in which R1 represents a linear or branched alkyl or alkenyl group, comprising from 7 to 18 carbon atoms, and R2 represents a linear or branched alkyl group comprising from 1 to 6 carbon atoms, and -one or more non-siliceous fatty substances. The invention also relates to a cosmetic treatment process using the said composition, and to the use of the said composition for cosmetic treatment of the hair.
