Pat the chicken thighs dry with paper towels. In a bowl, combine maple syrup, Dijon mustard, minced garlic, salt, and pepper. Add chicken thighs, coat thoroughly, and let marinate for at least 15 minutes.

While chicken marinates, peel and cube sweet potatoes into 1-inch pieces. Toss sweet potato cubes with olive oil, salt, and pepper until evenly coated.

Preheat oven to 425°F (220°C). Arrange marinated chicken thighs and seasoned sweet potatoes on a baking sheet, ensuring space for roasting. Roast for about 30 minutes.

After 15 minutes, flip chicken thighs for even cooking. Baste with remaining marinade for extra flavor.

Once chicken reaches 165°F (74°C) internal temperature and sweet potatoes are tender, remove from oven. Let rest for a few minutes before serving.