Preheat your oven to 350°F (175°C). Grease a 9x5-inch loaf pan or line with parchment paper. Mash bananas with a fork.
In a bowl, whisk together flour, baking soda, salt, and cinnamon.
In another bowl, whisk melted butter and brown sugar until smooth. Add eggs and vanilla, mixing well.
Stir in mashed bananas.
Add the dry ingredients to the wet mixture, stirring until just combined.
Gently fold in blueberries.
Pour batter into the prepared loaf pan. Scatter a few extra blueberries on top for a pretty finish.
Bake for 50–55 minutes, or until a toothpick inserted in the center comes out clean.
Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely. Slice and enjoy!