At the age of 40 he converted to Christianity and in 325 he convened the first ecumenical Council of Nicaea. Because of the importance of this council, many people believe that Constantine created the Church, but in fact there had been many councils (though not as large) prior to Nicaea and the structure of the Church already existed. Constantine was at the council merely as an observer and the Bishops and representative of the Pope made all of the decisions.
Sa edad na 40 siya convert sa Kristiyanismo at sa 325 siya convened sa unang ekumeniko Konseho ng Nicaea. Dahil sa kahalagahan ng konseho na ito, maraming tao ay naniniwala na Constantine nilikha Simbahan, ngunit sa katunayan doon ay naging maraming mga konseho (bagaman hindi bilang malaki) bago ang Nicaea at ang istraktura ng Simbahan nabubuhay sa mundo. Constantine ay sa konseho lamang bilang isang tagamasid at ang Bishops at kinatawan ng Papa ginawa ang lahat ng mga desisyon.