A park spokesman said the rocks fell from El Capitan, a rock formation above Yosemite Valley, on to a popular hiking trail shortly before 14:00 local time (21:00 GMT).
The park remains open and visitor services are not affected.
El Capitan is the world's largest granite monolith and one of the best-known landmarks in Yosemite.
In a statement, the park said the rockslide occurred in an area popular with climbers.
"The release point appears to be near the 'Waterfall Route', a popular climbing route on the East Buttress of El Capitan," it said.