Hardy, who finished with 19 points, started his drive near midcourt, went past one defender on the right side of the court only to find another one there. He went to the baseline and underhanded the ball up and over the rim to give the Red Storm (17-9, 9-5 Big East) another highly ranked victim in Madison Square Garden.
St. John's beat then-No. 13 Georgetown, No. 9 Notre Dame, No. 3 Duke and No. 10 Connecticut, all big wins in the eyes of the NCAA tournament selection committee and the Red Storm are looking for their first bid since 2002.
Ashton Gibbs, who missed the last three games with an MCL injury to his left knee, came back in a big way for the Panthers (24-3, 12-2), who had won five straight overall and five in a row over St. John's.
The junior guard finished with a career-high 26 points and was 6 of 9 from the 3-point line, matching Pittsburgh's total number of 3s in his absence.
The win is the sixth in seven games for St. John's and all of them have been with coach Steve Lavin and his staff wearing white sneakers and no ties. They started the look in the win over Duke and plan to keep it the rest of the season.
Hardy's game-winner was the eighth lead change of the second half and it was tied five times. It was also the Red Storm's only field goal in the final 6 minutes as they went 10 of 12 from the free throw line in that span.
Travon Woodall hit the only 3 not from Gibbs with 11.3 seconds left to give the Panthers a 59-58 lead.
After a timeout by Pittsburgh, St. John's started the final play and Hardy, who has scored over 30 points twice in the last five games, delivered.
Gibbs, the sixth-leading scorer in the Big East with a 16.3 average, didn't start but he had 15 points in as many minutes in the first half.
His 3.2 3-pointers per game is sixth in the nation and 46.3 percent accuracy from behind the arc is seventh in the nation. He missed the Panthers' wins over West Virginia, Villanova and South Florida.
Without Gibbs, the Panthers were 6 of 29 on 3s, well off their 38.3 percent that leads the Big East.