Saturday, the restaurant moves across the street to 57 East Main St., according to a sign on the current location's door on Thursday.
"Thank you all for your support and patience during this time, and we can't wait to see you at 57 East Main St.!" the sign said.
The Bistro plans to re-open in mid-September, owner-executive chef Stephen Chitow told Westborough Patch.
The move to the Downtown Crossing space vacated by the Bangkok Thai Restaurant has been in the works for months.
Chitow first discussed it with Westborough Patch in late December 2012.
The Bistro has rented space at 72 East Main St. for more than 16 years, starting May 15, 1997, Chitow has said.Chitow had searched for larger space for two years.
The new site offers the business a full kitchen; 50 to 60 seats, compared to 19 now; and space for a breakfast case, he said.