Star relaxes with US actor in Italian Riviera
Earlier this week, a topless Sienna was snapped kissing the Brothers And Sisters star on a luxury yacht.
And now the 26-year-old, who split from Rhys Ifans, 39, last month, has been seen hugging Balthazar, 33.
Balthazar is believed to be giving Sienna tips on the best areas to buy a house in Hollywood.
SEE PICS Sienna Miller on holiday with Balthazar Getty here>>