His first paper was published in 1970 and focused on Hugh O'Neill, 2nd Earl of Tyrone and in the subsequent years additional examinations of Gaelic Ulster followed.
In 1967 Canny was awarded the Ford Foundation fellowship to travel to the United States and carry out a PhD in History in the University of Pennsylvania.
In addition, he has built hugely on David Beers Quinn's thesis of Ireland as a practising ground for English colonial policy in the Americas.
This study was the basis of his PhD in the United States and Canny's research on this topic has demonstrated the extent of these parallels in a manner previously under appreciated.
Canny's debates with fellow historians, Brendan Bradshaw of Cambridge University and Ciarán Brady of Trinity College, Dublin, on why the Reformation failed to reform more than 20% of the population of Ireland, and on the ideology of Edmund Spenser, have been major additions to historical debate in recent decades.