A pedestrian was struck by a train just east of Weston GO station, disrupting service on the Kitchener GO Train line and the UP Express.
The incident happened around 6:30 a.m. on Thursday.
The pedestrian was rushed to hospital with serious injuries.
GO buses were operating an express service from Union station to Pearson International Airport during the suspension.
Full service resumed on both the GO Train and UP Express lines just before 9 a.m.