Begin by combining the softened cream cheese, sour cream, granulated sugar, and vanilla in a mixing bowl. Use a hand mixer to create a velvety, seamless blend.
In a separate smaller bowl, mix the walnuts together with the brown sugar.
Add the grapes to the cream cheese mix, and use a spoon to mix the grapes into the creamy mixture.
Scoop the grapes into a serving bowl, and sprinkle the walnut and brown sugar mix on top.