She is expected to leave easyJet around the end of the year but in the meantime will continue with her existing responsibilities.
The search for her successor has already commenced and easyJet said it expects to select from a “strong range of candidates”.
John Barton, easyJet chairman, said: "Carolyn built and led the management team that has transformed easyJet’s performance in every respect since 2010.
"She put easyJet’s passengers and people at the heart of the business. Having first built a solid operational performance, she redefined the customer experience not just at easyJet but across short-haul Europe and has seen both the number and loyalty of easyJet’s passengers grow as a result.
"This has led to sustained and continuing financial success which has been shared with shareholders with a more than trebling of easyJet’s share price and the payment of £1.2 billion in dividends.
"She will leave easyJet well set for future success. Her successor will inherit a leadership team of strength and depth, engaged people and loyal passengers flying on Europe’s best network.
"I speak for absolutely everyone at easyJet in saying we will be sorry to see Carolyn leave and that we wish her well in her exciting new role."
McCall said: "This was a really difficult decision for me to make. I have had an amazing seven years at easyJet, I am so proud of what the airline and its people have achieved in that period.
"After seven years, the opportunity from ITV felt like the right one to take. It is a fantastic company in a dynamic and stimulating sector.
"EasyJet is a structural winner in a brilliant position, and I look forward to being a loyal customer in the years to come.”
easyJet’s third-quarter trading update will be issued on Thursday July 20.
The airline expects to report that an improving revenue per seat trend, as outlined in the half year results in May, has been supported by strong third quarter load factors, as well as the continued reduction in market capacity growth and a significant benefit from the move of Easter to April.
Full year cost per seat at constant currency expectations remain in line with guidance “reflecting continued strong cost control with planned investments in resilience to support the delivery of improved operational performance during the summer months”.