Preheat oven to 325 degrees F (165 degrees C). Grease and flour a 10-inch Bundt pan.
In a large bowl, stir together cake mix and sugar. Make a well in the center and pour in eggs, cream cheese, oil and vanilla. Beat on low speed until blended. Scrape bowl, and beat 4 minutes on medium speed. Stir in blueberries. Pour batter into prepared pan.
Bake in the preheated oven for 40 to 45 minutes, or until a toothpick inserted into the center of the cake comes out clean. Let cool in pan for 10 minutes, then turn out onto a wire rack and cool completely.