A method for sterilizing closure elements (3) for packaging containers (1), wherein the closure elements (3) are collected individually by a holding mechanism (25) in the region of a sterile chamber (12) and are placed onto an opening (4) of a filled packaging container (1) and connected to the latter, and wherein the closure elements (3), while being conveyed inside the sterile chamber (12), are treated by means of at least one sterilizing medium (6, 7, 52) during a sterilizing process.