Preheat your oven to 350°F (175°C). Grease a loaf pan.
In a mixing bowl, combine mashed bananas, melted butter, and sugar.
Add beaten eggs and vanilla extract, mix well.
In another bowl, whisk together flour, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, stirring until just combined.
Gently fold in the blueberries.
Pour the batter into the prepared loaf pan.
Bake for 60 minutes, or until a toothpick inserted into the center comes out clean.
Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.