Begin by preheating your air fryer to 375°F (190°C) for about 5 minutes.
While the air fryer is heating, wash the Brussels sprouts and trim the ends. Cut them in half lengthwise and place them in a mixing bowl.
Drizzle the olive oil over the Brussels sprouts, then sprinkle with garlic powder, onion powder, salt, and pepper. Toss everything together until the Brussels sprouts are evenly coated.
Once the air fryer is preheated, spread the Brussels sprouts in an even layer in the air fryer basket. Make sure not to overcrowd the basket; you may need to cook in batches if necessary.
Cook the Brussels sprouts in the air fryer for 15 minutes, shaking the basket halfway through to ensure even cooking.
Once done, check if they are golden brown and crispy; if not, add a few more minutes as needed.
If desired, sprinkle with grated Parmesan cheese right before serving for added flavor.
Transfer the Brussels sprouts to a serving platter and enjoy them hot!