Travis Cook, 53, was accused of stabbing 43-year-old James R. Parsons IV multiple times in the chest around 10:52 p.m. Monday on a train near the Clinton Blue Line station, officials said.
Parsons was taken to Stroger Hospital where he was pronounced dead, police said.
Cook was arrested less than 24 hours after the stabbing on the Near West Side.
He was charged with first-degree murder and one felony count of murder.
The deadly attack came hours after Chicago Police Supt. David Brown talked about the resources the department has dedicated to the city's transit system.
"We've added an additional 130 officers to the CTA since March to not only control the platforms but to also patrol our buses, our stops that drive violence," Brown said. "We've seen an increase in arrests recently."