Abstract: Device (100) for reconstituting an active ingredient in sterile powder, comprising a vial (4) containing the active ingredient; a flexible bag (1) containing a sterile liquid; a connecting component (5) secured to the vial (4) and to the flexible bag (1); an elastomeric sealing ring (10) arranged between the connecting component (5) and the vial (4), an axially perforated spike (7), constrained to the connecting component (5), wherein a sterile chamber (70) is provided, delimited by the vial (4), by the connecting component (5) and by the sealing ring (10, 110), whereby the active ingredient is reconstituted in sterile conditions.