Abstract: A protective doorknob encasement device which provides a protective cover over the space formed between a door jamb and an exterior doorknob to prevent insertion of a tool to forcibly open the door. The invention includes a mounting plate and a track guide to enable slidable attachment of a protective casement. The track guide is configured so as to orient and restrict movement of the casement along the track and only in a direction toward the exterior door surface. Removal of the casement is permitted by its continued forward motion along the track and is only possible when the door is open. This unidirectional forward motion results from use of spring-biased pawls coupled to the casement which catch in corresponding grooves set in the mounting plate to prevent rearward motion. An opening is provided in the casement in alignment with a key slot of the enclosed doorknob to permit normal access.