Jay-Z, who earlier took to social media and stopped a concert to press Mill's case, penned an op-ed for The New York Times to call for a concerted campaign to reform probation.
"What's happening to Meek Mill is just one example of how our criminal justice system entraps and harasses hundreds of thousands of black people every day," Jay-Z wrote.
"Instead of a second chance, probation ends up being a land mine, with a random misstep bringing consequences greater than the crime," wrote the 47-year-old rap mogul, who said he saw the same ordeals as a poor teenager in Brooklyn.
A judge in Philadelphia last week sentenced Mill to two to four years in prison for parole violations, raising audible gasps in the courtroom as prosecutors had not recommended any incarceration.
Mill, who is signed to Jay-Z's Roc Nation management, has been appearing before the judge since a 2008 arrest on gun and drug possession charges.
The judge pointed to recent incidents including an altercation involving Mill at the St. Louis airport, although the now 30-year-old rapper was not charged.
His case has generated growing protests including a rally by hundreds of supporters outside the Philadelphia courthouse.
Mill said he was badly beaten by police when they arrested him in 2008 and used a bloodied mugshot of himself as the cover of his "DC4" mixtape.
His most recent album, "Wins and Losses," went to number three on the US chart earlier this year.
Probation, which dates from English common law, was initially seen as a compassionate way for courts to grant freedom to people who pose little risk.
But a recent survey by The Marshall Project, a non-profit news organization that covers the US judicial system, found that at least 61,250 people and probably far more are in prison across the United States for minor parole violations such as missing appointments, failing drug tests or staying out past curfew.
"The system treats them as a danger to society, consistently monitors and follows them for any minor infraction -- with the goal of putting them back in prison," Jay-Z wrote.
Of the 4.65 million people on probation, parole or supervised release across the United States in 2015, 30 percent were African American, according to Justice Department figures.
