The present invention relates to a cosmetic composition for the treatment of keratin fibres, particularly human keratin fibres such as hair, comprising, in a cosmetically acceptable medium, one or more organosilanes, one or more cationic polymers having charge density greater than or equal to 4 meq/g and one or more cationic surfactants. The present invention also relates to a cosmetic process for treating keratin fibres using said cosmetic composition. The present invention finally relates to the use of said composition for the cosmetic treatment of keratin fibres.