Jenna Fabian said she was on her way to work when the fire broke out around 8:30 a.m. in the 11700 block of West Wilshire Boulevard in the Sawtelle neighborhood.
The man, who has not been identified, was clinging to a window of the 25-story building.
"For a long time, you were wondering where's the ladder? They couldn't get to him, and eventually they do," Fabian said. "There were a bunch of people around me and we're watching this happen."
A short time later, firefighters used a ladder to rescue the man.
"There was a little bit of hesitation from both ends. I think they were a little too far away from each other and the guy was just hanging on, I don't know how," Fabian said. "But firefighters were able to move the ladder a little bit closer to him. This guy had started pretty far back and he climbed a good amount of the way to get to the right side of the building, to get away from the flames. I don't know how he did that and managed not to fall. But they got close enough to him where they were able to just grab him and pull him down safely."
Plumes of thick, black smoke continued to emit from broken windows, with flames charring a balcony and the exterior of the sixth floor.
At least eight people were treated at the scene, including a 3-month old child, Los Angeles Fire Department Chief Ralph Terrazas told reporters at the scene. One of those patients was in critical condition, and six suffered smoke in inhalation.
Terrazas confirmed there were no fatalities in the incident, and that no one had jumped from the building despite earlier reports.
The cause of the inferno is unknown, but investigators say the blaze has been ruled suspicious.