Yes, pea protein powder can be mixed with milk. In fact, it can be mixed with any liquid of your choice, such as water, milk, or juice, to create a protein shake. Pea protein has a mild, slightly earthy flavor that is neutral enough to blend well with a variety of liquids and flavors. Some people prefer to mix pea protein with almond milk, coconut milk, or oat milk, as these plant-based milks can help to improve the flavor and texture of the shake.