The incident occurred in the 1400 block of North Edgemont Street around 7:45 p.m.
Police say the woman had just finished working out at the building's gym. When she passed the laundry room on her way back to her apartment, police say, a man grabbed her, beat her up and tried to sexually assault her.
Investigators believe the suspect may be a transient. He ran off after the attack.
The woman was treated for scrapes and bruises.
Anyone with information was urged to call police.