In a small bowl, add chia seeds and ½ cup almond milk. Whisk until thoroughly combined. Cover and chill in the refrigerator for about 10 minutes.
Add bananas and remaining 1 cup almond milk to a blender. Blend until smooth, scraping down the sides of the blender as needed.
Add blueberries, blending until smooth.
Remove the chia seed mixture from the refrigerator—it should have thickened to a gel-like consistency. Whisk until well mixed. Using a rubber spatula or spoon, scrape the chia seed mixture into the blender. Blend until smooth.