"This is your dude, Spike Lee. And you know that I know that you know that the system is rigged! For too long we've given our votes to corporate puppets. Sold the okie doke. Ninety-nine percent of Americans were hurt by the Great Recession of 2008, and many are still recovering," Lee said in the ad released Tuesday. "That's why I am officially endorsing my brother, Bernie Sanders."
He is known for weighing in on current issues including Hurricane Katrina, police brutality in urban communities and the diversity issues in media.
Lee, an Academy Award nominee, has also been on the front lines in the recent conversation about the lack of diversity in Oscar nominees.
Former Secretary of State Hillary Clinton leads Sanders among black voters, a key voting bloc in South Carolina's primary on Saturday.
A recent CNN/ORC South Carolina poll
showed Clinton with 65% support from black voters, compared to 28% for Sanders.
Lee praises Sanders for his activism during the Civil Rights Movement, education policy and fight against income inequality.
"Bernie takes no money from corporations. Nada. Which means he's not on the tape, and when Bernie get's into the White House, he will do the right thing," Lee said. "Enough talk. Time for action."
Lee previously told CNN's Christiane Amanpour, "What would it say to the world if (Donald) Trump got elected?"
"When we go around the world saying, 'We're the beacon of democracy' and you know, with the Constitution and human rights and all that stuff, and that he's the president?" Lee said. "Look, there's no negating the fact that he's a great showman. But we're talking about the highest office in the United States of America. This is not a TV show."
Lee said he doesn't think the Republican front-runner should be trusted as commander in chief.
"The President has the guy next to him who got that box," he said, referring to the case containing the codes to launch a nuclear attack.
"I had a fund-raiser for the President. I saw the box. That's scary. It's even scarier if he" -- breaking into a laugh -- "I don't want Trump anywhere near that box. Nowhere near it."