Add the crushed tomatoes, Italian seasoning, garlic to the crockpot.
Drain the oil from the sun dried tomatoes, then add the the tomato mixture in the slow cooker. Pour in the alfredo sauce then mix everything together.
Lay the chicken breasts on top of the sauce and press down lightly so they are just submerged.
Cook on high for 2.5 to 3 hours, or low for 3 to 3.5 hours.
15 minutes before the sauce is ready, cook the fettuccini noodles in salted water, per package instructions.
Once the sauce is ready and chicken is cooked through, remove the chicken from the sauce and chop it into bite sized pieces.
Mix the chicken back into the sauce.
Stir the parmesan into the sauce, then toss sauce with the fettuccini.
Optional: garnish with chopped parsley and additional parmesan cheese.