No injuries were immediately reported.
The flames broke out in a closed Conway clothing store that is undergoing renovation. Authorities say the fire might have been started by workers.
Firefighters said it appeared there were workers in the store with torches.
It took crews just under 90 minutes to bring the fire under control.
The cause of the fire is under investigation.
West 34th Street was briefly closed in both directions between Sixth Avenue and Ninth Avenue.