Preheat your oven to 400°F. Line a baking sheet with parchment paper.
In a large bowl, combine ground chicken, breadcrumbs, Parmesan cheese, parsley, egg, garlic, Italian seasoning, salt, and black pepper. Mix until just combined; do not overmix.
Using your hands, form the mixture into meatballs, about 1.5 inches in diameter, and place them on the prepared baking sheet.
Bake the meatballs in the preheated oven for 20 minutes or until they are cooked through and golden brown.
Remove the meatballs from the oven and pour marinara sauce over them. Sprinkle shredded mozzarella cheese on top.
Return to the oven and bake for an additional 5-7 minutes, or until the cheese is melted and bubbly.
Serve warm, garnished with extra parsley if desired.