In short, yes!
The sippy cup base is microwave safe and you can place it directly into the microwave to warm milk or other liquids. never place the sippy cup lid with straw in the microwave as these are not microwave safe.
Also, please refer to ‘can I put warm liquid in my b.box sippy cup’ with regards to suitability for our various sippy cup styles. remember to always be cautious when serving warmed liquids to young kids, to ensure they are evenly heated and not too hot. as a guide, to warm milk – allow approx. 20 seconds per 180mls in the microwave.