Yes, the BRAZILIAN SILK™ Professional Treatment performs on hair extensions. It would be best for the stylist to perform the BRAZILIAN SILK™ Professional Treatment separately on the extensions prior to putting them into the hair. If you wish to perform the treatment on extensions that are already in the hair, the stylist will need to be extremely careful when applying the heat to the bonded area. If the stylist is careful and works to first separate the hair extensions from the client’s own hair, a great result can be achieved.