A protective cap for use with a medical fluid fitting including a fitting thread and a sealing portion having a sealing surface. The protective cap includes a body having a proximal end, a distal end, and a cap thread extending axially. The cap thread is configured to threadedly engage the fitting thread for releasably coupling the protective cap with the medical fluid fitting, and defines a tapered engagement surface. The tapered engagement surface tapers axially relative to a longitudinal axis of the body, and is configured to frictionally contact the fitting thread for retaining the protective cap in coupling engagement with the medical fluid fitting. The protective cap is configured to peripherally surround the sealing portion such that no portion of the protective cap contacts the sealing surface when the protective cap is coupled with the medical fluid fitting.