The Eagles will make the announcement at 2pm as their search for a new boss to replace Sam Allardyce has ended with the appointment of the former Ajax coach.
De Boer has been out of work since he was sacked by Inter last year after just three months when he won just five of 14 games in charge at the San Siro.
That came after a successful stint at Ajax, where the former Netherlands and Barcelona midfielder won four titles in six years.
The 47-year-old will become Palace’s third manager in the last 12 months.
The Eagles have been on the lookout for a new manager since Allardyce quit the club in May after leading them to Premier League safety.
After missing out on number one target Marco Silva who joined Watford from Hull, Palace chief Steve Parish has turned to the Dutchman.
Palace took to social media to suggest that an appointment was imminent, as they posted a video of white smoke billowing out of a Caribbean takeaway, echoing the method that the Vatican use to announce that a new Pope has been appointed.
De Boer’s twin brother Ronald spoke of Frank’s new role in an interview on Sky Sports News at the weekend:
“Frank is very excited, of course. It’s the biggest league – everybody knows it, everybody’s watching the Premier League.
“You can do really something if you have the chance, because there is money involved and you can buy players.
“It’s an interesting league to see what you’re capable of as a manager.
“I know they are talking and I think it’s just about little terms with the coaching staff. I don’t see any problem, but of course it’s not for me to say if it’s a done deal or not.”