Preheat your waffle iron according to the manufacturer's instructions and lightly grease it with butter or nonstick spray.
In a large mixing bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.
In a separate bowl, whisk together the buttermilk, eggs, melted butter, and vanilla extract.
Pour the wet ingredients into the dry ingredients and stir until just combined. Do not overmix; a few lumps are perfectly fine.
Gently fold the blueberries into the batter.
Spoon the recommended amount of batter onto the hot waffle iron and close the lid.
Cook for 4–6 minutes, or according to your waffle maker's instructions, until the waffles are golden brown and crisp.
Carefully remove the waffles and repeat with the remaining batter.
Serve immediately with your favorite toppings.