Pittsburgh Bureau of Fire responded to reports of a structure fire in the 3000 block of Vensel Way around 2:30 a.m.
The front of the 3-level structure was engulfed in flames when firefighters arrived.
All of the residents from each of the three apartments were able to safely evacuate the building and firefighters quickly extinguished the fire.
A firefighter suffered an ankle injury and was transported by medics to the hospital.
Zone 1 police officers were also on scene.
The Fire Investigation Unit is investigating the cause of the fire.