Preheat your air fryer to 350°F (180°C).
If your air fryer has a preheat function, use it to ensure it's properly warmed up.
Place the leftover chicken fajitas in the air fryer basket. Make sure to spread them out in a single layer for even reheating.
If desired, lightly spray the fajitas with cooking spray to help them get crispy. This step is optional but can enhance the texture.
Cook the fajitas for 3-5 minutes. Be sure to check them after 3 minutes to avoid overcooking. You're aiming to heat them through, not to fully cook them again.
Shake the air fryer basket or flip the fajitas halfway through the cooking time for even heating.
Once the fajitas are heated through and have reached your desired level of crispiness, remove them from the air fryer.
Serve the reheated chicken fajitas with your favorite toppings, such as guacamole, salsa, sour cream, and shredded cheese.