"I know he is a leader, not just to beat Donald Trump, but to bring honor back to that office," Booker said about Biden in an interview with CBS News.
The Democratic party primary contest has narrowed to a two-man race between Biden and Vermont Senator Bernie Sanders, and both candidates campaigned Monday ahead of another round of voting on Tuesday.
Biden's campaign surged last week after he won the resounding support of black voters in key contests from South Carolina to Texas.
"African-American voters in the South, African-American voters here in Detroit, they have played a pivotal role in my entire lifetime in choosing the Democratic nominee," Booker said.
Michigan, which votes on Tuesday, is seen as another test of whether Biden can muster a coalition of African-American, suburban, and older primary voters to his cause.