Preheat the oven to 350°F (175°C).
Line a muffin tin with paper liners or grease with cooking spray.
In a mixing bowl, combine mashed bananas, granulated sugar, and brown sugar.
Add melted butter and mix until well combined.
Beat in the egg and vanilla extract.
In a separate bowl, whisk together the baking soda, salt, and flour.
Gradually add the dry mixture to the wet mixture, stirring gently until just combined.
Fold in the blueberries carefully.
Divide the batter evenly among the muffin cups, filling them about 2/3 full.
Bake for 20-25 minutes or until a toothpick inserted in the center comes out clean.