Muga Apondi of Kenya's high court said he was giving a "light" punishment since Cholmondeley had been in prison for nearly two and a half years and that he had showed concern for the victim after he had shot him.
"I hereby sentence the accused to eight months in prison," Apondi said.
"I hereby wish ... to impose a light sentence on the accused to allow him to reflect on his life."
Cholmondeley has only admitted to shootings dogs on his ranch.
Protesters in court shouted in outrage as the judgement was read, some raising placards saying the justice system favoured the rich.
Cholmondeley, the great-grandson of Lord Delamere, formerly one of Kenya's biggest landowners and one of its most prominent early settler families from Britain, was found guilty of manslaughter in the 2006 killing on his family's ranch.
The case had ignited resentment among many black Kenyans angry at the extent of white land ownership more than 40 years after the country gained its independence from Britain.
Much of the Kenya's best land was taken over by the British government during colonial times.
After independence in 1963, many departing settlers transferred the land to Africans, with Britain underwriting some of the costs, but some, including Cholmondeley's family, kept their land and became Kenyan citizens.
A previous murder case against Cholmondeley, in which he was accused of killing a wildlife ranger in April 2005, was dropped due to lack of evidence, sparking an outcry from many Kenyans.