In some of the cases, his victims were restrained.
Baltimore police Sgt. Thomas Allers referred to it as "taking lunch money."
He admitted to participating in at least nine robberies between 2014 and 2016 that yielded more than $100,000 in cash, prosecutors say.
In one incident, Allers arrested robbed a man named Davon Robinson for $10,000.
After robbing his home, Allers released Robinson.
Prosecutors say Robinson was killed after he was unable to pay back a drug debt.
"Allers released detainees and chose not to charge them criminally when he stole cash from them," prosecutors wrote in Allers' indictment.
In another incident, Allers' adult son, who is not a police officer, participated in a raid in which $66,000 was taken by Allers, his son and two other detectives.
Authorities have not named the son or charged him, according to court papers.
As part of his sentence, prosecutors recommended Allers pay over $117,000 in restitution to his victims.
Allers' defense attorney Gary Proctor said his client is an alcoholic who suffers from post-traumatic stress disorder from his years of policing Baltimore's streets.
"He’s a thoroughly decent person," Proctor said after Allers' sentencing.
Allers was the eighth cop indicted in the growing scandal that has consumed Baltimore's gun unit and the first convicted.
Seven other officers are accused of carrying out robbery and extortion campaigns stretching back three years, often targeting suspected drug dealers.
Allers had worked for the Baltimore Police Department since 1996.