Preheat the oven to 425°F (220°C).
Lightly grease a large sheet pan with non-stick cooking spray.
Slice the chicken, bell peppers, and onion into even strips.
Arrange the vegetables evenly across the pan and place the chicken on top.
In a small bowl, mix all the fajita seasoning ingredients until well combined.
Sprinkle most of the seasoning over the chicken and the remaining seasoning over the vegetables.
Add the minced garlic and drizzle the olive oil evenly across the pan.
Toss everything together until well coated, then spread into an even layer.
Bake the Sheet Pan Chicken Fajitas for 15–20 minutes, or until the chicken reaches an internal temperature of 165°F (74°C).
During the final 5 minutes, wrap the tortillas in foil and warm them in the oven.
Remove the pan from the oven, squeeze fresh lime juice over everything, and sprinkle with chopped cilantro.
Serve immediately with warm tortillas and your favorite toppings.