The 62-year-old manager's impressive grasp of tactics and team spirit will allow him to bring the Red Devils back to the top, says the former Netherlands midfielder
De Boer worked closely as a player under Van Gaal at club level with Ajax and Barcelona as well as with the Netherlands.
Van Gaal's Old Trafford tenure will officially get under way when the 62-year-old's time as Oranje coach finishes after the World Cup and De Boer is in no doubt that the veteran will immediately lift spirits at United following David Moyes's ill-fated spell in charge.
He told MUTV: "I think you are getting one of the best managers in the world so the chance of success is high.
"I believe that, especially when you have patience, he will get success because he's so determined to do well but also he has a great vision.
"On his tactics, he will know the weak points of the opponents and what the team needs so he can really make a very strong team and a team that believes in each other.
"Sometimes it takes time to get that belief from the players. Some will not accept that and will drop off but, when you have everybody together, believe me, you will have great success."