Peyton Siva scored 19 points for the No. 2 Cardinals (5-1) and Russ Smith added 17, but the No. 5 Blue Devils beat Lousiville 76-71 in the championship game of the Battle 4 Atlantis.
Duke and Louisville were so close for so long until Quinn Cook took charge.
The sophomore guard scored 11 of his 15 points in the final 7:46, including the Blue Devils' last eight of the game.
Neither team led by more than five points over the final 10 minutes until Cook's final free throw with 6.7 seconds left made it 76-71.
Peyton Siva brought the Cardinals back from an 11-point second-half deficit by scoring the first seven points of an 11-2 run that brought Louisville within 54-52 with 10:55 to play.
Louisville played without 6-foot-10 Gorgui Dieng. The shot-blocking center is out with an injured left wrist and his replacement, 6-10 Zach Price, scored the game's first basket, doubling his point total for the season. He finished with four points and three rebounds.
Even though the game had two of college basketball's greatest coaches in Duke's Mike Krzyzewski and Louisville's Rick Pitino, and was played in one of the world's playgrounds for the rich, it was the players who were the stars of the night.
The pace wasn't frenetic but it was upbeat. The work under the boards was rugged. There weren't many fans in the Imperial Arena, a grand ballroom turned into a basketball venue, who weren't on the edge of their seats or standing for the final 10 minutes.
Louisville hurt itself by missing four straight free throws in a 2-minute span until Chane Behanan made the second of two with a minute left to bring the Cardinals within 70-67.
The win was the 23rd straight in a regular-season tournament for the Blue Devils, a streak that dates to the championship of the 2006 CBE Classic.
Louisville had won the last four regular-season tournaments it was in.
Duke had lost its last three games to Louisville. The Blue Devils' previous win in the series was the 1986 NCAA championship game.