In a mixing bowl, combine the cooked shredded chicken, diced avocado, ranch dressing, diced tomatoes, diced red onion, chopped cilantro, lime juice, salt, and pepper. Mix until well combined.
Warm the flour tortillas in the microwave or on a skillet until soft and pliable.
Divide the chicken avocado ranch mixture evenly among the tortillas, spreading it down the center of each tortilla.
Top each tortilla with shredded lettuce and shredded cheddar cheese.
Fold the sides of the tortillas over the filling, then roll them up tightly to form burritos.
Serve the Chicken Avocado Ranch Burritos with sour cream and salsa on the side for dipping or drizzling.