The slide took place between Banff and the Bow Valley Parkway turnoff around 3:30 p.m. MT.
Both eastbound and westbound lanes of the highway had been closed, but both were open again as of early Saturday morning.
Traffic had been backed up along the stretch of highway, but no one was injured in the slide.
Eastern park gates open
RCMP had been advising against motorists heading west from Banff on the highway, and had closed down the park gates east of town Friday evening.
Motorists were being advised to turn around and head into Canmore or Calgary until the mudslide has been cleared.
While the park gates are now open, RCMP say motorists should travel with caution because debris from the mudslide may have caused slippery sections.
Banff National Park communications officer Mark Merchant said it is believed recent heavy rain caused the slide.
"Our first concern is to make sure there ... are no injuries, or anything like that. So that's our first concern is public and visitor safety," he said.
"After that, of course, it is getting this important transportation core open again as quickly as possible and stabilizing the scene to make sure it does not happen again."