It took hours for firefighters to get the scene under control in the Flatlands section.
The fire broke out around 1:00 Sunday morning at the corner of Flatbush and Flatlands Avenue.
Investigators said the fire started in a Chinese restaurant. It quickly spread through about a half-dozen stores.
Those businesses include a bagel store and a men's store that has been in business for 88 years.
"We're devastated," Anthony Balzofiore of Mac's Men Shop. "It's our livelihood. It's all we know. I've been working here since I'm 13 years old. So, hopefully, we can rebuild and be back somewhere in this neighborhood."
The building, built in the early 1900s, have common rooms that pre-date fire codes.
A hardware store next door to the destroyed businesses was left virtually untouched because it had a fire wall.
Firefighters continued to hose down hot spots on Sunday morning.