Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Trim the woody ends off the Brussels sprouts and slice each one in half lengthwise to ensure even cooking.
Pat the chicken breast completely dry with paper towels and season both sides with half of the salt, pepper, and garlic powder.
In a medium bowl, toss the halved Brussels sprouts with the olive oil and the remaining salt, pepper, and garlic powder until well coated.
Place the chicken and Brussels sprouts onto the prepared baking sheet, making sure to spread the sprouts out in a single layer with the cut-sides facing down.
Roast for 20 to 25 minutes until the chicken reaches an internal temperature of 165°F and the sprouts are tender with charred, golden edges.
While the tray roasts, combine the balsamic vinegar and honey in a small saucepan over medium-low heat, simmering for 3 to 5 minutes until the mixture thickens into a glossy glaze.
Slice the chicken into strips and drizzle the warm balsamic glaze over the crispy Brussels sprouts before serving.