The anticipated move comes despite continued uncertainty over whether non-essential foreign travel will be permitted from Scotland this year.
Ryanair plans to fly twice a week to the coastal resort on Wednesdays and Sunday from July 4, with tickets already on sale.
The summer service is due to continue until October 27.
Ryanair originally launched the route from Edinburgh in 2009.
The Zadar announcement follows the airline last week announcing new routes from Edinburgh to Naples from June 1 and to Knock from Sept 1, which were previously operated by other carriers.
Ryanair chief executive Michael O’Leary accompanied that by saying Scots could book flights abroad this summer with “reasonable confidence” because high vaccination rates “must result in the removal of restrictions”.
Edinburgh Airport said it remained unclear when holidaymakers would be allowed to fly abroad again.
Aviation director Kate Sherry said: "It's always exciting to announce new routes and we're delighted to be adding Zadar to our Croatian offering along with Split and Dubrovnik.
"We know people are looking forward to taking trips when conditions allow.
"We hope recovery plans will become clearer over the next few weeks and we will continue to plan to make sure we are ready for that."
The Scottish Government has said foreign travel would not possible until May 17 – and might be later.
Responding to Mr O’Leary last week, its spokesperson said: “We want travel to get back to normal as soon as it is safely possible, but as the First Minister has set out, we must move very carefully to ensure continued suppression of the virus.
"If we open up too much, too quickly then we risk a resurgence of the virus.
"We are clear that non-essential international travel will not be possible before the May 17 target date the UK Government has set, and our view is it might not be possible for a further period after that.
"Some restrictions and requirements, including testing, are likely to remain in place for some time."