Preheat your oven to 400°F. Line a baking sheet with parchment paper.
In a large bowl, combine 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, and place them on the prepared baking sheet.
Drizzle the olive oil over the meatballs. Bake in the preheated oven for 20-25 minutes, or until the meatballs are cooked through and golden brown.
While the meatballs are baking, heat the marinara sauce in a small saucepan over medium heat until warmed through.
Once the meatballs are done, remove them from the oven and serve them topped with warm marinara sauce and extra mozzarella cheese if desired.