A hair extension applicator (1), of the kind used to lengthen and/or thicken head hairs by applying additional hair extensions to natural hair, enables a strong precision and rapidity in use and comprises a handle (2), a pair of jaws (6,7) adjacent therebetween, supported on said handle (2), apt to receive therebetween a portion of head hair and one or more fixing elements of respective additional hair extensions, pressing member and respective actuation means (11) which determine the programmed translation of the pressing member (9) with respect to a contrast means.