The Wisconsin Election Commission on Monday reported that Biden won 64 percent of the vote to Sanders' 31 percent. A six-day delay in counting the votes was ordered by a state court to accommodate late mail-in ballots.
Wisconsin's was the last Democratic primary where voters had a choice between Biden and Sanders. Sanders ended his campaign last week and endorsed Biden on Monday.
Democratic-backed challenger Jill Karofsky defeated Republican-backed Judge Daniel Kelly, appointed by former GOP Gov. Scott Walker.
In a statement after the votes were tallied on Monday, Karofsky condemned the decision to hold the election amid the outbreak.
"Look, we shouldn't have had the election on Tuesday. It was an untenable decision, but the people of the state of Wisconsin rose up," she said. "Anyone who wasn't brought to tears when they were looking at those people in Milwaukee voting on Tuesday and voting in Green Bay on Tuesday, just doesn't have a heart."
The GOP-controlled statehouse and state Supreme Court blocked a last-minute effort by Democratic Gov. Tony Evers to delay the primary or send out ballots to every voter.
Because of the back-and-forth over the election, chaos reined when only five of Milwaukee's 180 polling places were open, meaning Wisconsin voters, wearing masks and trying to practice social distancing, lined up for hours last Tuesday.
After Wisconsin voted on Tuesday, 22 states still have not held primaries - Alaska, Wyoming, Ohio, Kansas, Nebraska, Georgia, Oregon, Hawaii, Connecticut, Delaware, Indiana, Maryland, Montana, New Jersey, New Mexico, Pennsylvania, Rhode Island, South Dakota, West Virginia, Louisiana, Kentucky and New York. Four territories have also yet to vote - Washington, D.C., Guam, Puerto Rico and the U.S. Virgin Islands.
Wisconsin reported 3,428 confirmed cases of COVID-19 Monday, with 154 deaths, according to the state health department's website.