Miller will join in July and succeeds Chris Haynes, who departs this month.
The appointment comes during a busy summer for the ECB, with an upcoming Cricket World Cup and the Ashes.
Miller brings more than 14 years of experience across corporate and consumer communications. She has held senior media roles at Engine, Mischief and Golin, and worked for more than seven years at William Hill, where she rose to PR director.
She has previously advised clients including The FA, Sport England, BAE Systems and Vodafone UK, and delivered award-winning work for The FA with The Emirates FA Cup and People’s Cup, in addition to Sport England’s campaign ‘This Girl Can’.
"This is a very significant appointment and a key role for the ECB and the whole game. Kate brings strong and relevant experience in what is a very broad and demanding role," ECB CEO Tom Harrison said.
"Her leadership, communication skills and campaigning experience from across the public sector and sport ensure that she is well placed to excel in this role.
"Kate joins at an exciting time for cricket in England and Wales, as we begin delivery of Inspiring Generations, the game-wide strategy for 2020-24 and begin wide-reaching new partnerships with Sky and BBC."
Miller said: "It’s a huge honour to be joining The ECB at such a significant time for cricket in England and Wales. A momentous summer awaits us, followed by pioneering change with next year’s launch of The Hundred.’’
Experienced consultant and former ECB employee Mark Ward will lead comms at the ECB in the interim period between Haynes’ departure and Miller’s arrival.
He has held senior communication roles with European Games, Tottenham Hotspur and UEFA.
Following the departure of Haynes, the comms team will report to COO David Mahoney.