Very airy and light cotton. The only problem for me is that the neck is a bit large (it's a Small already), so I will have to fix that, but it's a great sundress and I love the texture, feel and the lovely blues.
I bought the medium, 5'5" 150 lbs, and it fits perfectly. The button and crossover piece are lovely and add to the vibe. It is very comfortable and classy LOVE IT!