His feast day is formally an Eastern Orthodox holiday, although it is not commemorated with any special liturgy; there are two known historical "akolouthiai" for him, including an 1874 copy of an older Magnesian "menaion" for the month of November, which shows that in the 15th and 16th century, he was venerated as "the holy glorious equal of the Apostles and emperor John Vatatzes, the new almsgiver in Magnesia." The relevant hymns are preserved in only one known manuscript in the library of the Leimonos monastery on Lesbos, Greece, and include references to the feast day for the almsgiver John Vatazes. John III Vatatzes' feast day has largely fallen out of favor other than in the church dedicated to him in his birth city of Didymoteicho.