Preheat oven to 350°F and grease a 9x13-inch baking dish with nonstick cooking spray.
Pour both cans of peaches with their syrup into the prepared baking dish and spread evenly across the bottom.
Sprinkle the dry cake mix evenly over the peaches, then drizzle the melted butter over the entire surface of the cake mix.
Sprinkle cinnamon on top and bake for 45-50 minutes until the top is golden brown and the edges are bubbly.
Let cool for 10 minutes before serving warm with vanilla ice cream or whipped cream.