Preheat oven to 350°F (175°C). Line a muffin tin with paper liners or grease with non-stick cooking spray.
In a large bowl, whisk together flour, sugar, baking soda, baking powder, and salt.
In another bowl, mix mashed bananas, vegetable oil, Nutella, egg, and vanilla extract until well combined.
Pour the wet ingredients into the dry ingredients and stir until just combined. Do not overmix.
Spoon the batter into the prepared muffin tin, filling each cup about 2/3 full.
Bake for 18-20 minutes or until a toothpick inserted into the center comes out clean.
Allow muffins to cool in the tin for 5 minutes before transferring to a wire rack to cool completely.