The fire broke out on Totowa Avenue around 9 a.m., and the flames quickly spread through the three-story buildings before jumping to the neighboring structures.
About 100 firefighters from Paterson and surrounding towns, including Hawthorne and Fair Lawn, battled the blaze with heavy smoke conditions.
The apartments and first-floor businesses were heavily damaged, and the the buildings will need to be razed.
About a dozen residents are getting help from the Red Cross.
At least one person was treated for smoke inhalation, and two firefighters were also hurt.
The cause of the fire is under investigation.