Over the past centuries, manuscripts containing collections of folk recipes for the treatment of diseases were written mostly by Catholic priests in Croatia. They were used to prepare remedies and gave directions for their use. These writings provide valuable information for ethnographers and historians of pharmacy and medicine. They describe the types and frequency of diseases afflicting humans and domestic animals in the past, development of ethnopharmacology, folk medical terminology, names of medicinal herbs, and the interaction between folk and science medicine. This is why they need a multidisciplinary approach to be evaluated properly. This paper presents the 1776 Medicine Book by a priest Petar Kastelan from southern Croatia (Dalmatia). It was found in a private archive and has not yet been published. The collection is written in the Croatian Cyrillic script, which was mostly used from the Middle Ages to the second half of the 19th century by Catholic priests when they wanted to write in Croatian. The collection contains 250 recipes for human medical practice and 10 recipes for veterinary medical practice. Thirty recipes contain household advice. Materia medica of the manuscript is mostly composed of drugs of plant origin. Remedies of animal and mineral origin are also included, but to a smaller extent. Valuable information is given about the folk names for diseases and medicinal plants as well as descriptions of the ways of preparing remedies. Prayers for healing, void of sorcery and magic, are also included.