Preheat and prep. Preheat your oven to 350°F. Lightly grease a 9x9-inch baking dish with butter or cooking spray.
Mix everything together. In a large bowl, stir together the drained whole kernel corn, creamed corn, cornbread mix, sour cream, melted butter, and beaten eggs until well combined. The mixture will be thick and slightly lumpy.
Transfer to baking dish. Spoon the mixture into the prepared baking dish and spread evenly.
Bake. Bake for 45 minutes, or until the top is golden brown and a toothpick inserted in the center comes out clean.
Cool slightly and serve. Let the casserole rest for 5-10 minutes before serving. It will set up slightly as it cools.