This paper attempts to analyze the instances and contexts of the use of the concept “heart”, which is the key concept for Christian anthropology, based on the material of Old Irish church literature, namely, on the treatise Apgitir chrábaid. The following cases of using the word “heart” in the studied text are revealed: “love for God in the heart”, “fear of God in the heart”, “purity of the heart”, “simplicity of the heart”, “confession of something in the heart”, “heart as a container of faith” , “heart as the dwelling place of God”, “heart as the place where the Truth is”.