All three had cardiac arrests, police say.
Both of the deceased are adult males who were pronounced dead at area hospitals, according to officials.
John Fasula Jr., 50, was one of the deceased victims.
The third victim, who remains in critical condition, is an adult female. Paramedics had tried to resuscitate the woman in the lobby.
A firefighter, who suffered a minor injury, is in good condition, officials said.
Fire crews also treated other people at the scene. Black smoke was seen coming from the seventh floor of the building, where it began around 8:45 a.m. Tuesday. It's not clear how many units were damaged.
The Chicago Fire Department asked residents in other parts of the building to stay in their units because it was safer than going into the smoke-filled hallways and stairs.
"Some of the residents in the building we actually sheltered in place. In other words, there wasn't a need to take them into the smoke-filled hallways. There wasn't a need to bring them down ladders. We had a pretty good handle on the situation," said Commissioner John McNicholas, Chicago Fire Department.
Meanwhile, many residents stood and watched as the fire broke out on the 7th floor. One woman, who wishes to remain anonymous, was on the 11th floor, directly above the unit on fire. She- along with several other residents- waited for an hour on the frigid balcony.
"I could see the edge of the building, and I looked around. I could see the black smoke coming out of the building, and I knew that it was very serious," she said. "It was right under my bedroom, and the smoke was coming through the vents, I assume underneath the front door from the hallway."
Janice, who asked us not to use her last name, paced a small balcony for nearly 45 minutes. She tried to escape, but couldn't.
"My apartment eventually filled with smoke," she said. "The balcony was the last resort."
"When I reached the door to the stairwell there was someone there buckled over and said 'You can't get down, there's too much smoke.',"she said.
While some people stayed put, others were evacuated- wrapped in bath towels.
"We were sleeping, and we heard the alarm. And we were like ah it's nothing. And then we looked out the window and it was all smoky," said one woman.
As some attempted to escape, hallways and stairwells filled with smoke.
"All you saw was a big black cloud. That's it. You didn't see nothing else. Couldn't even see through the hallways or the stairways or anything," said Jay Fizer, building resident.
"I wasn't afraid at all because I knew what I was going to do. And that's get down the stairs. So I wasn't fearful," said Leslie Emery, building resident.
Officials say the fire was struck out in about 45 minutes.
"As quick as we could, we put guys on every floor, right above the fire floor and on the fire floor. They were able to knock down the fire rather quickly," said Commissioner McNicholas.