Associated with Kells and Connor in Dal Riada
Aengus MacNissi is reputed to have been baptised by St Patrick. He is associated with Kells and later with the district of Connor in Dal Riada. He seems to have become the leader of the Church, possibly a bishop.

Friend of Colman of Dromore
He was a friend of St Colman, whom he advised to set up a monastery in Dromore. There is a legend that he had such a venerationf for Scripture that he would not carry his Gospel book in a leather satchel, but carried it on his shoulders.

Patron of Down and Connor
Along with St Malachy, St MacNissi is patron of the Catholic diocese of Down and Connor. St MacNissi's College was opened as a residential college at Garron Tower on the north-east Antrim coast in the 1950s and remains a prominent second level college in the diocese.