Lewis will start his new role in the late summer of 2024, joining BT's executive management team and reporting directly to CEO Allison Kirkby.
He will lead all communications, brand and government relations.
In addition to corporate affairs, the role will assume responsibility for the BT Group brand and group insight team.
Lewis is currently a senior managing director in the global corporate affairs group of private equity firm Blackstone, where he has led European communications for almost four years.
Before that, he was head of communications at KPMG. He has also held roles at HM Treasury and Barclays Bank, where he was director of strategic communications.
Tom Engel will continue in post as interim group corporate affairs director until Lewis joins.