It wasn't pretty, but following a close overtime thriller, the Buckeyes will advance to the semifinals, something the Wildcats have never accomplished.
Northwestern, who lost by one point to Ohio State earlier in the year, had their chances to win this one but came up short late.
John Shurma led the Wildcats with 23 points and Michael Thompson chipped in 15, but Northwestern had no answer for Jared Sullinger who took over the late in the game.
The Wildcats did a great job of disrupting the Big Ten Freshman of the Year early in the game, but with the game on the line they had no answer for Sullinger, who went 16-for-18 from the line, finishing with 20 points and 17 rebounds.
As a team, the Buckeyes shot the ball poorly, going just 3-for-15 (20 percent) from deep and 19-for-59 (32 percent) from the field.
Buford and Diebler connected on just two of their 10 three-point attempts, by far their worse combined effort of the year.
Freshman Aaron Craft came up big off the bench, scoring 17 points and turning the ball over only once in 40 minutes of action.
Ohio State will face the winner of the Michigan vs. Illinois, whom the Buckeyes went a combined 4-0 against during the regular season.