The diploma thesis Wax seals on documents and their protection in conservation-restoration works includes a theoretical and practical part. The theoretical work describes the history and preservation of wax seals and their significant characteristics. In addition to seals, sphragistics is explained, which includes the history of sphragistics in Croatia, its development and what are the instructions for every sphragist. The last chapter of the theoretical work includes the seal book, which covers its creation and its history , conservation and restoration of wax seals, chemical composition and structure of wax and a recipe for making sealing wax.. The practical part describes the documentation during the conservation-restoration works on 3 manuscripts with wax seals written in iron-gal ink, which are the property of the Dubrovnik Diocesan Archives. In the practical part, the found condition of the document is briefly described, a historical-artistic treatment is made and a list of proposed works that serve as a guideline for carrying out interventions on the documents is made. The graduation work initiated the understanding of the importance of wax seals, because they are an important part of every document. They contain a printed, engraved character or figure on a thin flexible material made of cellulose fibers, that is, a flat product obtained from an aqueous suspension of cellulose fibers. Since preventive protection is a part of overall protection and is the basis of heritage preservation by reducing and slowing down deterioration, every documentation after conservation and restoration works also contains instructions and suggestions for preserving objects from further deterioration.