The Eredivisie champions came from behind to beat Manchester United 2-1 in their opening group game of the Champions League this week.
And De Boer believes PSV have shown Ajax the way they must approach the game if they are to take maximum points from the visit of Ronny Deila’s men.
“PSV showed how it needs to be done. It’s up to us to show that tomorrow. Tactics are important, but it’s more important that you play with your heart,” he said.
“Celtic can make things difficult for us. It won’t be easy, but I think we can win this. We often get results against British clubs, because they want to play football. That creates space for us.”
De Boer confirmed that defender Johnny Heitinga was not fit enough to make the squad for the game but centre-back Jairo Riedewald has complete confidence in Ajax’s strength in depth.
“We have a good team. Everyone has the same goal, which is to reach the next round,” said the 19-year-old.