Baptists visiting London heard him preach and invited him to Dublin in 1747. Around this time he was in the process of joining the Moravians. After differences with his Dublin hosts, he concentrated his attentions on Ulster, where he founded some 220 Moravian societies between 1747 and 1752 and helped to establish Evangelicalism in Ireland. A plaque on the wall of the Moravian church in Gracehill, County Antrim, commemorates the arrival in Ballymena on 9 August 1746, of John Cennick, the first Moravian evangelist in mid Antrim.