The decision to not use the BBC to broadcast the events is seen as a rejection after heavy criticism of its coverage of the Queen's Diamond Jubilee celebrations in 2012.
The BBC's reporting of the river pageant resulted in 5,000 complaints to the broadcaster, including its decision to use Fearne Cotton as one of the lead hosts.
However, the organiser refused to deny that the BBC's jubilee coverage was the reason the national broadcaster will not provided coverage of the birthday celebrations.
"We've worked with ITV before, and have complete confidence in ITV's ability and we are looking forward to working with ITV. Is that a political answer?" said Simon Brooks-Ward, the event's organiser, to the Times newspaper.
The show at Windsor will be a four-day extravaganza, running on May 12-15. It will feature 550 horses and 1,200 participants including musicians, dancers, choirs and famous actors, actresses and artists. It will also include members of the royal family who will attend the show each night.
The Queen, whose actual birthday is on 21 April, will attend the final performance.
The Queen has been informed of the plans and has given them her approval.
Singer Katherine Jenkins will be performing at the event next May.
The event will be extra special, as it will mark out the Queen as Britain's longest-reigning monarch.
The show will portray the Queen's life, from her childhood to the Second World War and her several state trips. The participants will include the Omani cavalry with more than 100 horses, and performers from Chile, Canada, South Africa, New Zealand, Australia, Azerbaijan and Fiji. There will also be state carriages from the Royal Mews.
The event is sponsored by companies including BT, Waitrose, and Jaguar Land Rover. Any surplus funds will go to the charities supported by the Queen.
"We have been delighted with the level of response from funders and participants. It should be a very special and memorable occasion," Brooks told ITV.