Place the frozen sliced peaches in the refrigerator overnight to thaw completely. This will ensure they are ready for use when you start baking.
Preheat your oven to 350 degrees Fahrenheit (175 degrees Celsius) to ensure it reaches the right temperature for baking.
Lightly grease the inside of a medium-sized casserole dish with butter. You can use a dish that measures approximately 7 inches by 11 inches.
In a large saucepan, combine the thawed peaches and 1/2 cup of sugar. Gently stir to mix them together.
Place the saucepan over medium to medium-low heat, add 4 cups of water and bring the mixture to a low boil. Allow it to simmer gently for 7 to 10 minutes, stirring occasionally.
Once the peach mixture has simmered, remove it from the heat.
Use a large slotted spoon to lift the peaches from the juice and transfer them to the prepared baking dish. Be sure to reserve the juice for later use.
Measure out 1/2 cup of the reserved peach juice and pour it evenly over the peaches in the baking dish.
Sprinkle the Jiffy golden yellow cake mix evenly over the peaches in the baking dish.
Evenly sprinkle 1/4 cup of sugar over the cake mix.
Sprinkle 1/4 teaspoon of ground cinnamon over the entire mixture in the baking dish.
Use a butter knife to gently make swirls in the baking dish, combining some of the dry ingredients with the peach juices below.
Drizzle the melted butter evenly over the top of the cobbler mixture in the baking dish.
Place the baking dish in the preheated oven and bake the cobbler at 350 degrees Fahrenheit for approximately 35 minutes.
Bake until the top is golden brown and set, indicating that it's fully cooked.
Once baked, remove the cobbler from the oven and allow it to cool slightly before serving.
Serve the delicious Jiffy mix peach cobbler warm, either on its own or with a scoop of vanilla ice cream for an extra treat!