The bodies were found around 9 am today at a house on Pacific Hills Drive, said sheriff's Lt. Jeff Hallock.
The circumstances of the deaths were under investigation and no identifications were immediately released.
The house is located in a development called Pacific Hills, a modern neighborhood of two-story, upscale homes on winding streets.
Mission Viejo is a city of about 95,000 in the southern section of Orange County about 80 kilometres southeast of Los Angeles.