In this paper, the author seeks to reconstruct the linguistic worldview of ‘joy’ appearing in the Canticle of the Sun written by St. Francis of Assisi. During the reconstruction, it caused a special difficulty that the word ‘joy’ did not occur explicitly in the work under investigation, so the contents referring and related to it could only be examined indirectly. The need to place the Canticle in a broader context made it inevitable to outline the era and include certain biographical elements, and the complexity of the analysis required the application of linguistic-historical, textological, translational and theological aspects in addition to the literary ones during the investigation. The analysis of the work was carried out by including the original Italian version of the text and its English translation together, by exploring the psychological and theological deep layers of the poetic images used by St. Francis and by presenting the mythological content associated with them. During the investigation, the author of this paper came to the conclusion that the primary source of joy that fills St. Francis as he sings about creatures in his Canticle is actually not of this world, but transcendent.