Place pecans in a skillet over medium-low heat; cook and stir until pecans are toasted and fragrant, 3 to 5 minutes.
Remove from heat and pour into a heatproof bowl; stir to prevent nuts from overcooking.
Beat sugar, cream cheese, and vanilla extract together with an electric mixer in a bowl until smooth. Fold in pecans and grapes. Stir gently until grapes are coated.