The building is made of brick with a flat tin roof. The fire entered the roof space, which was difficult to access.
Firefighters fought the blaze from inside and outside the building and brought it under control about 8.15pm.
It appeared no one was home in the four affected apartments on the top floor, while the other residents managed to self-evacuate.
Paramedics attended the scene and treated one man who was taken to The Alfred hospital in a stable condition.
The MFB remained on the scene overnight.
A spokeswoman said on Thursday morning all apartments remained uninhabitable and residents stayed in alternative accommodation overnight.
The cause of the fire is still being investigated.