Definitely! If you end up with loads of leftovers, or if you would simply like to make extra, freezing is an excellent option for chicken spaghetti.  Make sure that you allow the casserole to cool all the way before packaging it up. Stored in airtight freezer-safe containers, leftover Tex Mex spaghetti will last for up to 2 months in the freezer.  For smaller amounts of leftovers, store in the refrigerator in an airtight container for around 3-5 days.