Packaging device (10, 110) for a cosmetic product, comprising: - a cosmetic product reservoir (12, 112), comprising an internal volume and an opening providing access to said internal volume; - a neck extending along an axis passing through the opening, between an edge of the opening and an end; - a seal (14, 114), comprising a tubular assembly portion (28, 128) inserted in the neck; and - a cover (16, 116), that can be removably assembled to the reservoir in a closed position; said cover comprising a closing element (62, 162) capable of cooperating with the seal so as to close and seal the opening in the closed position; the seal also comprising a tubular shaped skirt (30, 130) for receiving the closing element, said tubular shaped skirt (30,130) being arranged along the axis, the seal (14,114) further comprising a ring axially adjacent to the assembly portion (28,128), said ring coming into axial stop against the end of the neck, the device being characterized in that said tubular shaped skirt (30,130) comprises a free edge oriented towards the exterior of said reservoir,the free edge being elastically deformable in the radial direction relative to said axis; in that said closing element (62,162) is configured to radially deform said free edge in the closed position; and in that the device is configured such that a free annular space (45, 178) is formed around the tubular shaped skirt (30, 130) in the closed position, sc as to enable the free edge to stretch during insertion of the closing element (62, 162) in the tubular shaped skirt (30,130) to the closed position, for ensuring a sealed closure of the reservoir. - a cosmetic product reservoir (12, 112), comprising an internal volume and an opening providing access to said internal volume; - a neck extending along an axis passing through the opening, between an edge of the opening and an end; - a seal (14, 114), comprising a tubular assembly portion (28, 128) inserted in the neck; and - a cover (16, 116), that can be removably assembled to the reservoir in a closed position; said cover comprising a closing element (62, 162) capable of cooperating with the seal so as to close and seal the opening in the closed position; the seal also comprising a tubular shaped skirt (30, 130) for receiving the closing element, said tubular shaped skirt (30,130) being arranged along the axis, the seal (14,114) further comprising a ring axially adjacent to the assembly portion (28,128), said ring coming into axial stop against the end of the neck, the device being characterized in that said tubular shaped skirt (30,130) comprises a free edge oriented towards the exterior of said reservoir,the free edge being elastically deformable in the radial direction relative to said axis; in that said closing element (62,162) is configured to radially deform said free edge in the closed position; and in that the device is configured such that a free annular space (45, 178) is formed around the tubular shaped skirt (30, 130) in the closed position, sc as to enable the free edge to stretch during insertion of the closing element (62, 162) in the tubular shaped skirt (30,130) to the closed position, for ensuring a sealed closure of the reservoir.