Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Wash the Brussels sprouts, trim the woody ends, and cut each sprout in half vertically.
Dice the chicken breast into uniform 1-inch cubes to ensure even cooking.
Place the halved sprouts and chicken cubes on the prepared baking sheet.
Drizzle with olive oil and sprinkle with sea salt, black pepper, and garlic powder.
Toss everything together directly on the pan until the chicken and vegetables are thoroughly coated in oil and spices.
Spread the mixture out into a single layer, ensuring the Brussels sprouts are mostly cut-side down for maximum caramelization.
Roast in the center of the oven for 20 to 25 minutes, tossing halfway through, until the chicken is cooked through and the sprouts are tender with crispy, golden-brown edges.
Remove from the oven and immediately drizzle the balsamic glaze over the hot chicken and sprouts.
Toss gently to coat and serve warm.