In a series of tweets, the senator said that the “jury’s verdict delivers accountability for Derek Chauvin, but not justice for George Floyd”.
He wrote: “Real justice for him and too many others can only happen when we build a nation that fundamentally respects the human dignity of every person.
“The trauma and tragedy of George Floyd’s murder must never leave us. It was a manifestation of a system that callously devalues the lives of Black people.”
Mr Sanders added that “our struggle now is about justice – not justice on paper, but real justice in which all Americans live their lives free of oppression”.
“We must boldly root out the cancer of systemic racism and police violence against people of color,” he tweeted.
Mr Sanders tweets follow the verdict in the case on Tuesday where the jury found the now-fired officer, Derek Chauvin, who is white, guilty of second-degree unintentional murder, third-degree murder and second-degree manslaughter.
The guilty verdict for Chauvin has led to nationwide celebrations with many people seen hugging and cheering. In several parts of Minneapolis, people cheered and honked car horns after the verdict.
At George Floyd Square, the crowd that had gathered was overwhelmed with relief but many said more needed to be done following recent cases of people of colour being shot by police.
The officer will be sentenced at a separate hearing due to take place in about two months.
On 25 May last year, in Minneapolis, George Floyd was stopped on suspicion of using a counterfeit $20 bill for a pack of cigarettes at a corner shop. While the police were trying to put him in a squad car, Floyd panicked and pleaded that he was claustrophobic.
Instead, the police put him on the ground. A video recorded by a teenager showed that Chauvin placed his knee on Floyd’s neck for about nine and half minutes, including for several minutes after Floyd’s breathing had stopped and he had no pulse. The incident had led to a series of Black Lives Matter protests across the US and the world.