Add the banana, strawberries, blueberries, almond milk, Greek yogurt, ice and sweetener (if using) into your blender.
Blend until all ingredients are combined and the mixture is smooth. If the smoothie seems too thick, add a little more almond milk and blend again.
Pour your smoothie into a glass and enjoy immediately. If you wish, you can garnish the glass with a slice of strawberry or a few whole blueberries for an extra touch.