A brake booster device is provided for a braking system of a vehicle having an input rod component, which may be situated relative to a brake actuation element in such a way that the input rod component is adjustable with the aid of a driver brake force exerted on the brake actuation element, and having a guide body with a bore formed therein, into which the input rod component at least partially protrudes, an initial spring being compressibly arranged between an inner wall of the bore in the guide body and a widened intermediate section of the input rod component, and the initial spring being constrained with the aid of a captive spring mount.