She will be tasked with reconciliation in violent conflict and comes with experience in peace-building and dialogue.
Previously, she worked at an organisation linked to the United Nations to use religion to bring about peace.
She takes over from Canon David Porter who is now Chief of Staff and Strategy to the Archbishop.
Canon Porter had also played a key role in the Church of England's Shared Conversations about human sexuality.
Archbishop Justin said: "I am delighted that Sarah Snyder will be my Advisor for Reconciliation. Sarah brings a wealth of experience and many gifts to the role which will enrich both her reconciliation work and the senior team at Lambeth Palace.
"I am also grateful for the continued partnership with Coventry Cathedral where my reconciliation ministry will continue to be based.
"Events in recent weeks remind us that reconciliation is more of a priority than ever. This is the hope we offer in the good news of Jesus."