Preheat oven to 350.
Drain two cans of the fruit cocktail. In a bowl, mix together the two cans of drained fruit cocktail and the third can (fruit + light syrup). Pour the fruit mixture into a 9 x 13 baking pan prepared with non-stick baking spray.
Spread fruit into an even layer. Sprinkle the dry cake mix over the fruit and spread into an even layer.
Drizzle the top of the cake mix with the melted butter, trying to cover as much of the top of the cake mix as possible. Sprinkle with nuts.
Bake for 48 - 52 minutes until the top of the cake is browned and the filling is gently bubbling around the edges. (Test with a toothpick to make sure there is no raw/liquid batter.)