There is not much information about Metropolitan Ioann I. According to one sources, he headed the Kyiv Metropolitanate from 1019, in the first years of the rule of Prince Yaroslav the Wise; according to other sources – not later than 1008. In 1008 the Metropolitan Ioann built two stone churches: one in the name of the Holy Apostles Peter and Paul at Berestove in Kyiv, and another at Pereyaslav (now
Opinions about his origin also differ. Some researchers hold he was a Greek, but basing upon the fact that on July 14, 1021, he found and honoured the relics of Rus Princes Borys and Hlib and established the day of their commemoration, we could assume that he was a Rus. Some researchers consider him to be a Bulgarian.
He is considered the author of the service celebrated on the day of memory of the Holy Martyrs Borys and Hlib. He is known not only from mentions in written sources but also thanks to the find of a lead bull of “Ioann the Metropolitan.”