Sirhan did not to attend the parole board hearing and did not send anyone to represent him.
Tip Kindel of the California Department of Corrections and Rehabilitation said that the board found Sirhan continues to be a danger to public safety and is not suitable for parole.
The board concluded Sirhan killed Senator Kennedy in a "cold, calculated and callous manner" with disregard for the senator and those with him.
Psychiatric exam results presented to the board indicated that Sirhan "hates Americans and, if released, wants to be involved in Middle East politics."
It was the 13th time Sirhan was denied parole.
He was sentenced to death after his conviction for killing Mr Kennedy, however ths was commuted to life imprisonment in 1972 as the death penalty was ruled unconstitutional by the California Supreme Court.
The death penalty was reinstated after the law was modified.
The Los Angeles district attorney and police department opposed parole. It will be five years before Sirhan can next be considered for parole.
The Palestinian immigrant shot Senator Kennedy after he won the California presidential primary.
Sirhan reportedly killed the New York senator because he backed selling war planes to Israel.