Yellow Line service was temporarily halted and Red and Purple Line service was delayed after the accident.
No injuries were reported.
The train derailed while approaching the Howard station at 7519 N. Paulina St. about 2:10 p.m., according to CTA spokesperson Catherine Hosinki.
The three passengers on the two-car train were able to go to the head car and get off onto the platform, CTA spokesperson Tammy Chase said.
Chase said it's "too soon to say" what caused the derailment.
Bus shuttles were running to accommodate Yellow Line customers, Hosinki said. Customers can also take the No. 97 Skokie bus.
The Sun-Times Media Wire contributed to this report.