Pemsel, who has worked as the chief executive of the creative agency Boymeetsgirl and as the managing partner of St Luke's, will take responsibility for ITV's overall brand strategy and for all on- and off-air marketing.
He will report to Clare Salmon, who has been promoted to the new role of director of marketing and commercial strategy. Salmon will oversee programme publicity and ITV's new viewer insight function, in addition to working with the sales team on advertiser strategy.
Pemsel's appointment reflects an increased emphasis on marketing across ITV's network of channels. He will manage the broadcaster's relationships with the creative agency M&C Saatchi and the media agency MindShare.
The marketing shake-up follows recent changes at ITV that saw the departure of Mick Desmond, the chief executive of ITV Broadcasting, and the appointment of Ian McCulloch as the broadcaster's commercial director. Gary Digby has replaced Graham Duff as the managing director of ITV Sales.
Salmon said: "David's appointment reinforces our strategy of putting advertisers and viewers at the very heart of ITV's business. We have put our money where our mouth is by taking on a senior marketer who really understands how to identify and serve the needs of both consumers and advertisers."
Pemsel said that his key challenge was to "keep ITV's iconic brand relevant and powerful in the digital age".