Preheat the Air Fryer. Preheat your air fryer to 375°F. This will ensure it's hot and ready to cook your candied carrots.
Prepare the Carrots. Peel the carrots and slice them into rounds of relatively uniform thickness, about 1/4 inch thick. This ensures even cooking.
Coat with Brown Sugar. Sprinkle the brown sugar and, if desired, the ground cinnamon over the butter-coated carrots. Toss them well to ensure they're coated with the sugar.
Air Fry the Carrots. Place the coated carrot rounds in the air fryer basket in a single layer. You may need to cook them in batches if your air fryer has limited space.
Air Fry. Cook the carrots at 375°F for about 10-15 minutes, shaking the basket or tossing the carrots halfway through the cooking time. The exact time may vary depending on the air fryer model and the thickness of your carrot rounds.
Check for Doneness. The candied carrots are ready when they are tender and the sugar has caramelized, giving them a glossy appearance. Make sure they are not too soft but still have a slight bite.
Serve. Once done, transfer the candied carrots to a serving dish and serve them while they're warm.