Sims had 28 points and nine rebounds, and Harris added 24 points and five assists to help the Wolverines beat 15th-ranked Ohio State 73-64 on Sunday.
Sims and Harris were the only scorers during a late 11-0 run.
"Your fear with Michigan is Harris and Sims getting going at the same time and that's what they did tonight," Buckeyes coach Thad Matta said. "They made big plays."
Sims' layup with 6 minutes to play sparked the run that gave the Wolverines (7-6, 1-1) the lead for good. Harris added a three-point play 30 seconds later that brought the sellout crowd to its feet.
"It does a lot," Harris said. "Beating a ranked team does a lot for our confidence."
He and Sims teamed for 25 points Thursday in a loss at Indiana but finished Sunday's game a combined 22 for 34 from the floor.
"We needed a lift and those two gave it to us," Wolverines coach John Beilein said.
The Buckeyes (10-4, 0-2) led 55-54 after P.J. Hill's 3-pointer with less than 7 minutes to play, but Michigan quickly answered and went on to beat Ohio State for the second time in 11 meetings. The visitors missed five straight shots while the Wolverines pulled away.
The drought was part of a second half that saw the Buckeyes shoot 28 percent from the floor. They were just as bad (27 percent) in the second period Thursday in a conference-opening loss at Wisconsin.
Jon Diebler scored 17 points to lead Ohio State, which lost consecutive games for the first time this season and played its sixth straight game without leading scorer Evan Turner. He might not return until early February.
"We had some extremely good looks," said Diebler, who had just three points in the second half. "We just didn't knock 'em down.
"They made big shots and we didn't."
While Ohio State struggled from the floor, Michigan finished the second half 15-for-23 (65 percent) from the floor. Sims had 18 points in the final period -- 16 of which came from the field.
"My teammates got me the ball where I can score," he said. "I was the recipient of a lot of good passes tonight."