The male bicyclist was riding north on Highway 1 south of Coast Road when it appears a car also traveling north struck the victim from behind, CHP officials said.
The victim and his bicycle were pushed off the right shoulder and down an embankment where he suffered fatal injuries, according to the CHP.
The dog was uninjured.
The vehicle fled in an unknown direction after hitting the bicyclist.
Authorities believe the car is a 1999-2002 model vehicle, possibly green with moderate front-end damage and a broken right headlight and possibly a broken right turn signal.
The killed bicyclist was found later in the morning around 10:40 a.m. by a passing bicycle rider.
The CHP reported the bicyclist did not have proper safety equipment.
Anyone with information about the collision is asked to call CHP officers M. Contreras or S. Jackson at (831) 662-0511.
The bicyclist's identity is being withheld, pending notification to his family, according to the Santa Cruz County coroner's office.