The present invention relates to a cosmetic composition comprising:-at least 0.1% by weight, relative to the total weight of the composition, of one or more fatty-chain alkoxy silanes of formula (I) below: R1Si(OR2)3 (I) 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 cationic polymers. The invention also relates to a cosmetic treatment process using the said composition. This composition can be used in particular for haircare, and especially facilitates the conditioning of the hair.
