Place the trimmed and halved Brussels sprouts in a large mixing bowl. Add the melted butter, olive oil, minced garlic, salt, and black pepper. Toss until the sprouts are evenly coated.
Arrange the Brussels sprouts in a single layer in the air fryer basket or on the rack. Dice the bacon and sprinkle evenly over the top.
Cook in the air fryer at 400°F for 5 minutes.
Open the air fryer and toss the sprouts for even browning, then sprinkle the grated Parmesan cheese over the sprouts.
Continue cooking in the air fryer at 400°F for an additional 4 to 6 minutes until the sprouts are tender and slightly crispy, and the bacon is fully cooked. Serve immediately while hot.
Notes
Be careful not to overcrowd your air fryer. Everything should fit in a single layer for best results.