Three of the four tracks were affected by mud, soil and bricks that came down an embankment just south of the Glenwood Station.
Delays of up to 30 minutes were reported on the Hudson Line during the morning commute, as crews worked to clear away the debris.
Two tracks were out of service and a third had a 30 mile per hour speed restriction going past the slide.
MTA Bus sent buses to the four stations most impacted by the landslide - Riverdale, Ludlow, Glenwood and Greystone - for customers going northbound from those stations.
For the afternoon, southbound trains could incur 5- to 10-minute delays as they will be using bridgeplates across Track 1 (the one with the mud) at the four affected stations.
Northbound trains will be discharging customers on the regular platforms, but on the opposite (inbound) side for faster unloading.