Whisk lemon juice, olive oil, Dijon mustard, garlic, salt, and pepper together in a bowl. Set marinade aside.

Place chicken thighs into a large resealable plastic bag. Pour marinade over chicken and seal bag, making sure to cover all parts of chicken. Refrigerate for at least 2 hours.

Preheat an air fryer to 360 degrees F (175 degrees C).

Remove chicken from marinade and pat dry with paper towels. Place chicken pieces in the air fryer basket, cooking in batches if necessary.

Fry until chicken is no longer pink at the bone and the juices run clear, 22 to 24 minutes. An instant-read thermometer inserted near the bone should read 165 degrees F (74 degrees C). Squeeze a lemon wedge over each piece upon serving.