Add cream cheese, sour cream, sugar, and vanilla to a large bowl and beat until smooth.
Fold in grapes and transfer to your serving bowl. Cover and refrigerate.
Right before serving, sprinkle with brown sugar and pecans.
Notes
STORE Grape Salad leftovers in an airtight container in the fridge for 2-4 days. The longer it sits, the softer the grapes may become. For the best texture, add the toppings just before serving.