The Most Rev Justin Welby will officiate the highly anticipated ceremony in May, but, even as the most senior cleric in the Church of England, he still experiences concerns.
He told ITV News that forgetting the order of the wedding vows or misplacing the ring - both mishaps he has suffered before - are possibilities which he will strive to avoid.
And, from a career perspective, the stakes could hardly be higher - the grandmother of the groom is the only person senior to him in the church.
The Queen is the supreme governor of the Church of England and this week gave her formal consent to the marriage of Harry and Ms Markle, an American actress.
Asked about his preparations for the approaching nuptials, Mr Welby said: "Unlike recent weddings, I must not drop the ring. And I must not forget to get the vows in the right order, as I did at the rehearsal for one of my children's weddings.
"At the heart of it is two people who have fallen in love with each other, who have committed their lives to each other with the most beautiful words and profound thoughts, who do it in the presence of God, through Jesus Christ, you pray for them to have the strength to fulfil their vows.
"And you seek to do it in a way that respects their integrity and honours their commitment."
The Archbishop reportedly sparked panic at a service last year when it became apparent one of the wedding rings had slipped from his grasp.
It was eventually located by the bride under a chair, it was previously reported.
Ms Markle recently made her own preparations for the wedding when she was formally introduced to the Anglican faith.
She was baptised and confirmed into the church during a ceremony led by the Archbishop of Canterbury at the Chapel Royal.
"It was very special, it was beautiful and sincere," Mr Welby told the broadcaster.
"And very moving. It was a great privilege."
Harry and Ms Markle will tie the knot at St George's Chapel in Windsor Castle on 19th May.
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