Michael Curry thought his invite to preach at the Royal wedding was an April Fools' joke, he told ITV's Good Morning Britain.
The presiding bishop of the US Episcopal Church preached a 14-minute sermon on love that was hailed as one of the stand out moments of the day.
It left the 800-strong congregation stunned and was the most tweeted about moment of the whole day.
But Curry said he initially thought the invitation to preach was a prank.
'I thought somebody was doing an April Fools' joke on me. I just didn't in my wildest imagination...' he told the morning breakfast show.
He added he 'had no idea' that his sermon had made such an impact. 'When I sat down from the sermon I remember thinking to myself, "I hope that was OK",' he said.
Asked on CNN what he was motivated by in writing the sermon, he said: 'If we could just harness the real power of love we could actually change and transform this world. That is was what was driving me. I'm convinced this is the case. That is really what Jesus of Nazareth was getting at and was willing to die for.'
He added: 'At its root this love is a sacrificial way that seeks the good and wellbeing of others sometimes even over and above one's own self interest.'