It serves the Metra Electric Line north to Millennium Station and south to University Park, Blue Island, and South Chicago.

[2] As of 2018, 18th Street is the 226th busiest of Metra's 236 non-downtown stations, with an average of 23 weekday boardings.

[1] The station is also occasionally served by South Shore Line trains from Gary and South Bend, Indiana, on an exceptional basis for Chicago Bears home games during football season.

As part of a non-compete agreement with Metra, eastbound South Shore trains can only board passengers at stops along the Metra Electric, and westbound trains can only discharge passengers.

The station was originally built by the Illinois Central Railroad (ICRR).