The winger has missed the Netherlands' two Group E victories with a hamstring problem so far as his team-mates breezed into the last 16 by beating Denmark and Japan.
The Bayern Munich man seems to be nearing full fitness ahead of Thursday's dead rubber with Cameroon in Cape Town and the coach will let Robben decide himself whether he can play.
"I am going to leave him to make the decision," said Van Marwijk. "He knows his own body best and he will let me know when he is ready.
"It can be in the next game or it can be in the knockout phase. He must take the decision. I'd prefer that he is used only when he is fit."