In a large bowl, combine chicken, spinach, half of the mozzarella cheese, and Italian seasoning. Toss or gently stir to combine.
Lightly grease or line a 9"x13" baking dish. Pour about a half cup of the Alfredo sauce into the bottom of the pan.
Cover the Alfredo sauce in the baking dish with a layer of lasagna noodles (I used 3 for each layer, 12 in total)
Spread a third of the the chicken mixture on top of the lasagna noodles, gently and evenly spreading. Then pour a quarter of the Alfredo sauce over the chicken mixture, spreading evenly. Place another layer of lasagna noodles on top.
Repeat step 4 two more times to use up all of your ingredients. You should have three filled layers when you're done, with lasagna noodles on top.
Pour remaining Alfredo sauce on top and cover with remaining cheese.
Place in a 350 oven for 45 minutes to an hour, until cooked through and top is golden and bubbly.
Remove from oven and allow to sit for at least 10 minutes before serving.