The Albion supporters joined the United faithful in applauding the retiring Ferguson, who was also revered with a guard of honour formed by both sets of players, and van Persie felt it was a nice touch for a man ending a remarkable career.
"After 26 and a half years at United and, before that, at Aberdeen, Sir Alex deserved it," said the Dutchman.
"He's unbelievable and what the West Brom fans did was a nice touch.
"It's right to show respect. It doesn't always happen in football but, today it did and I'm glad."