Preheat your oven to 400°F. Line a baking sheet with parchment paper.
In a large mixing bowl, combine the ground chicken, breadcrumbs, Parmesan cheese, mozzarella cheese, parsley, egg, garlic, Italian seasoning, salt, and black pepper. Mix until well combined.
Using your hands, form the mixture into meatballs, about 1.5 inches in diameter. Place the meatballs on the prepared baking sheet.
Drizzle the olive oil over the meatballs to help them brown in the oven.
Bake the meatballs for 20-25 minutes, or until they are cooked through and golden brown.
While the meatballs are baking, heat the marinara sauce in a small saucepan over medium heat.
Once the meatballs are done, remove them from the oven and add them to the saucepan with the marinara sauce. Gently toss to coat the meatballs in the sauce.
Serve the cheesy chicken Parmesan meatballs warm, garnished with additional parsley if desired.