Forward Dewan Huell's follow-up dunk with 41 seconds remaining gave Miami a 73-71 lead in overtime, and the Hurricanes (15-4, 4-3 ACC) held on despite missing key free throws down the stretch.
Walker also had a crucial block in the closing seconds to seal the win.
Huell finished with 18 points and 12 rebounds, and Ja'Quan Newton had 12 points for Miami.
Guard Quentin Snider scored 18 points to lead Louisville. Forward Anas Mahmoud had 15 points, and guard/forward Deng Adel scored 13. The Cardinals (15-5, 5-2 ACC) saw their winning streak snapped at five games.
Louisville scored the first six points of the second half to assume a 44-37 lead, but the Hurricanes quickly responded and caught up at 51-51 less than eight minutes into the period.
It was a back-and-forth affair from there to the end with no more than three points separating the teams until the final minute of overtime when Miami owned a brief four-point lead.
Louisville led 69-67 after Mahmoud missed the second half of a one-and-one, and Walker tied it for Miami with a driving layup with 4.8 seconds remaining. Adel's long jumper at the buzzer bounced off the rim, leaving the teams deadlocked at 69 at the end of regulation.
Both teams had trouble finding their range early. The Hurricanes made only two of their first dozen field-goal attempts while the Cardinals made only four of their first 12. That was good enough to give the Cardinals an early 13-8 lead, but Miami responded with an 11-0 run for a 19-13 lead approaching the midway point of the first half.
The two teams then started connecting. Louisville caught up 31-all and took a 38-37 lead into the locker room at the break.
--Field Level Media
Louisville | Miami-Florida | |
Quentin Snider 18 | Scoring | Lonnie Walker 25 |
Quentin Snider 3 | Assists | Chris Lykes 4 |
Ray Spalding 13 | Rebounds | Dewan Huell 12 |
Deng Adel 4 | Free Throws Made | Ja'Quan Newton 8 |
Ryan McMahon 2 | Steals | Bruce Brown 3 |
Ray Spalding 5 | Blocks | Bruce Brown 3 |
Team | Points | FG% | 3PM-3PA | FTM-FTA | Assists | Rebounds | Blocks | Steals | Turnovers |
Louisville | 75 | 41.5 | 5-22 | 16-25 | 8 | 35 | 10 | 9 | 11 |
Miami-Florida | 78 | 36.9 | 6-22 | 22-31 | 13 | 48 | 7 | 8 | 14 |