As it is usual to represent him in neo-Hispanic art, the beloved disciple appears as a young and beardless man, wearing a green tunic and a red mantle. The figure of the author of the fourth Gospel appears sitting in a forced posture of Mannerism descent. In his left profile, he has violent twists in the body and his head is in a three quarters position; while, in right profile, his torso is turned in opposite direction till he is in three quarters position in left profile. His legs return to the direction marked by the head, one leg is extended and the other is bent. His head is slightly raised and his gaze is lost in heaven, while he holds a pen with his right hand and, with his other hand, holds a book that refers to his Gospel. The Gospel lays over a flat surface of the rock that is in the left side of the composition and that is used as a desk, where there is also an inkwell. In the bottom left angle, in front of that rock, it can be devised the inseparable eagle, with which Saint Joseph is identified, posing on earth with its profile.
The figure of the saint, moved to the left of the composition, follows a diagonal axis that descends from left to right, an axis that repeats itself in short distance and parallel in the mountainous profile that serves as a background in this section. Towards the right side, the painter has arranged in several planes of depth a landscape, which has included, in addition to the fronds of some trees and the slopes of mountains that in the distance are cut out on the wide cloudscape, a river that in its undulating path is forming several waterfalls. In a part of it, it is guessed the diminutive scene of the baptism of Christ, under the manifestation of the Eternal Father who appears in a break of glory by the upper right corner of the composition.