This icon of Saint John the Theologian is the most venerated icon of the Μonastery. According to tradition, it is a donation of Emperor Alexios A΄ Komnenos to Hosios Christodoulos. The original painting is dated in the 12th century, but was completely covered by a re-painting during the 15th century. A reference to this icon exists in a codex of 1200, listing the items found at the monastery’s Treasury.
The Theologian is portrayed in bust, slightly turning to the right, while holding a gospel with both hands. The gospel and the Theologian's nimbus are enamelled, while the repoussé border of the icon is covered with silver and gilded laminates, dated in the 12th century. The hypothesis of the overpainting is enhanced by the fact that the 12th century nimbus does not exactly fit the Theologian’s head, suggesting that the original painting was covered by a later one. The icon's inscription was painted by monk Daniel the Cretan in the 19th century. The overpainting of the 15th century, attributed to Cretan cycles, seems to have altered the original scheme of the representation only in a few minor details. The position of the Theologian, the enhancement of the emotional state, as well as the exaggeration of facial features, like the large forehead, emphasized in an attempt to express spirituality and wisdom, are characteristics of the mannerist style of the last phase of the 12th century. The border of the icon, 9,5 cm wide, is covered with a decorative net of equal rhombs, each containing a flower in relief. This decorative ground is interrupted by fourteen medallions of outstanding art, each containing the bust of a saint.