To make these Chicken Parm Stuffed Shells gluten free, use certified gluten-free jumbo pasta shells and gluten-free breadcrumbs. Also confirm that the marinara sauce, shredded cheeses, and shredded chicken are free from hidden gluten-containing additives if needed for strict dietary requirements. If using pre-cooked or store-bought chicken, check labels carefully, as some seasoned or packaged chicken products may contain gluten.