Authorities said an argument led to the stabbing at about 4:45 a.m. They said a woman was standing near a staircase waiting for her boyfriend when man approached her. He initally insulted her, but it then turned violent.
"At some point, her boyfriend walked up the stairs, observed what was going on, engaged the suspect and they got into a fight," said L.A. City Sheriff's Capt. Dan Cruz.
During the fight, the suspect stabbed the two victims and then ran from the station.
The victims were aided by a man wearing a clown suit, one of several people at the station dressed in Halloween costumes after attending parties. They were rushed to local hospitals, where they were listed in stable condition.
A search was under way for the suspect, who was described as a 25-year-old black man, 6 feet tall and about 200 pounds.
The station was closed to commuters while investigators gathered evidence, and trains bypassed the station.
This is the third stabbing incident at a Metro station in recent months.
A 59-year-old man was stabbed to death on a Red Line train near the Hollywood and Vine station in August. And just a week later, a fist fight escalated into a stabbing on a Metro Gold Line train at the Memorial Park Station.
The incidence of serious crime on Metro trains is very low and deputies patrol the stations regularly.
"It makes me feel way safer because, you know, even if you want to do something, if you see a police officer... you feel safe," said subway rider Marina Martirosyn.
But this latest stabbing is cause for concern.
"It kind of worries me to think that trying to save gas could become dangerous like this," said subway rider Maurice Dedeaux.
Last week, the Metro Board approved funding that will allow authorities to increase staffing and visibility at train station.