The sheriff's department also discriminated against African-Americans in its enforcement of a housing voucher program, the Justice Dept. said.
The findings were specific to deputies in two stations in the Antelope Valley
Among the findings were that sheriff's deputies were more likely to stop African-Americans than whites and they engaged in a "pattern of unreasonable force."
"Our investigation showed significant problems in LASD's Antelope Valley stations," said Roy Austin Jr., deputy assistant attorney general.
"Although we disagree with many of the conclusions in the DOJ report, we look forward to working closely with the DOJ's Office of Community Oriented Policing Services Technical Assistance Unit to assess what, if any, changes and proposed recommendations need to be implemented," said sheriff's spokesman Steve Whitmore.
The government and Los Angeles County have reached preliminary agreements to make broad changes to policing in the Antelope Valley and to enforcement of the housing voucher plan. Some of the reforms include revising training and use-of-force policies as well as participating in community meetings to gauge feedback from residents.
The investigation dating to August 2011 involves the Sheriff's Department's Lancaster and Palmdale stations in the Mojave Desert north of Los Angeles.
The Associated Press contributed to this report.