James Deontae Davis, 24, must also spend five years on probation. He apologized to the victim, Steven Utash, his family and the city of Detroit for the attack.
Utash, a white tree-trimmer who lives in a Detroit suburb, was beaten by a group of 10 to 20 men after he hit a boy with his pickup truck in April. Police said Utash was not at fault because the boy, who survived the crash with a broken leg, ran in front of his truck.
A prosecutor objected strongly to Davis' relatively short sentence. But Wayne County Circuit Judge James Callahan said he had heard "an honest expression of remorse and apologies."
"I know the city's already got a bad name, and I know that incident that took place, that I joined in, didn't make the city look any better," Davis said. "I don't want my whole life to be judged on that one moment."
The two members of Utash's family who were in court did not say anything. On Monday, when the first three defendants in the case were sentenced, family members gave statements on the attack, including one from Utash that was read by his daughter.
Wonzey Saffold received a sentence of six to 10 years Monday, and Bruce Wimbush Jr., 18, got probation. A juvenile was also given a probationary sentence.
Latrez Cummings, 19, was set to be sentenced Thursday, but his hearing was delayed.
The defendants could have faced hate crime charges if the case had gone to trial.
In his statement, Utash, 54, said he can no longer drive or work and is unable to make his own decisions about finances. He was in an induced coma for 10 days after the beating .