They pushed a 46-year-old man to the ground and beat him under the platform in the 900 block of West Belmont around 4:30 a.m., Chicago police said.
They stole his belongings and then went to the Red Line platform, where they beat another man, 49, and took his belongings, police said.
Both victims were taken to hospitals with minor injuries.
The trio — two men, 18 and 24, and a woman, 20 — were arrested and charges were pending, police said.
The area near the Belmont Red Line has been the scene of three consecutive nights of violence.
After the Pride Parade Sunday, crowds descended on Lake View and three people were shot and three people stabbed in separate incidents. Another person was stabbed near the Red Line stop during an argument early Monday.
The next night, on early Tuesday, a large group of people crowded the streets of again, with video showing people dancing on top of a police car and a CTA bus as officers tried to contain the disturbance. Police said someone smashed a squad car’s windshield.