An applicator for cosmetic product, in particular mascara, has a twisted core (12) and fibres that extend radially from the core (12) in directions substantially orthogonal to said core. The fibres held by the core (12). The fibres form at least one envelope (E) by means of their free end, the envelope extending in a longitudinal extension direction around the core (12), referred to as the main axis X. The envelope (E) has a zone (Z), along the main axis (X), in which the fibres are deflected so as to produce a local deformation (F1-F4) of the envelope.