Si! Certo! There is even some contemporary art.
Generally speaking, your best bet for seeing modern era artworks would be to pay a visit to the Museo di Novecento in Florence. You can read about it and see some works here.
For a rundown on the modern sculpture that appears here and there throughout the city, see:
One of my favorite sculptures around town is an Art Deco treatment of the Madonna and Child; its on a building near the Palazzo Vecchio.