In the much anticipated meeting between these two Argentinian rivals some 6,000 miles from home, the finely poised final was clinched by River Plate after a nervy extra time in Madrid.
In an eventful first half which saw both teams nervous in attack and boisterous in defence, it was Boca Juniors who struck first through Dario Benedetto's composed finish as he took on Franco Armani in the River Plate goal to take the lead just before half time.
Despite sitting 11th in the league, it was River Plate who looked the better team for most of the game but it was their inability to find one of their own in the final third which was their setback - often finding an opposing player or even the advertising boards surrounding the Bernabau.
River's eventual equaliser came through Lucas Pratto who had finally been given a clear sight of the target following a quiet night for the striker. River had been persistently threatening the Boca defence and the former Boca player fired home to an exposed net with 68 minutes on the clock.
But the game needed extra time for a winner and it was well worth the wait. Boca had gone down to 10 men following Wilmar Barrios' second yellow, but a cool and calm control by substitute Juan Quintero with a thunderous drive from the edge of the penalty area, cannoned off the crossbar into the net.
Victory was sealed for River as Martínez ran the ball into an empty net with Andrada left in the wrong penalty area having gone up for a corner, concluding this electric affair.
Key Talking Point
River Plate were arguably wrongly not awarded a penalty with just over half an hour remaining in Madrid with Boca still hanging on to a 1-0 lead.
After a looping ball was sent into the box, River striker Lucas Pratto was first to get to the ball ahead of keeper Andrada, but in doing so, raised his boot towards the face of the Boca keeper who took out the striker without touching the ball.
River demanded a penalty as the keeper got nothing of the ball but protests were waived away by the official who awarded the free kick to Andrada, who only two months previous had been out with a broken jaw.
Starting XI: Armani (7); Maidana (7), Montiel (7), Pinola (7), Casco (7); Ponzio (6), Enzo Pérez (6), Fernández (7); Martínez (8), Pratto (7), Palacios (6)
Substitutes: Lux, Quarta, Zuculini, Quintero (6), Mayada (6), Mora, Alvarez.
It seems a cop out to give 'star man' to a goal scorer, but River Plate played collectively well as a team and a single outstanding player was difficult to single out.
Striker Pratto had to be patient and wait until 20 minutes remained until he could finally get a shot on target, and he cooly buried it past Andrada in the Boca goal.
River had dominated much of the play throughout the fiery encounter, probing the Boca defence but continuously failed to capitalise on some exhilarating build-up play.
It was a fairly uninspiring game for 36-year-old Leonardo Ponzio who was substituted with just over half an hour remaining.
The Argentinian's main contribution to the game was picking up a yellow card as he failed to really make an impact in the frantic game of football.
Key Talking Point
The opening goal was always going to be key in this gargantuan battle and first blood went to Boca through Benedetto, who was bizarrely replaced by Ramon Abila with half an hour remaining.
The striker ran between two River defenders after a sublime through-ball by Nandez, to meet Franco Armani one-on-one, but cooly slotted past the helpless goalkeeper to score his fifth goal of the competition and send Boca fans into ruptures at the Santiago Bernabéu.
The goal came after just after a moment of madness from Boca keeper Andrada as he almost handed River a free shot at his exposed net after his attempt to keep the ball in play fell straight back to River who failed to capitalise.
Starting XI: Andrada (7); Buffarini (6), Izquierdoz (6), Magallán (6), Olaza (6); Nández (7), Barrios (6), Pablo Pérez (8), Villa (6); Pavón (7), Benedetto (8)
Substitutes: Rossi, Goltz, Jara, Gago, Abila (6), Zarate, Tevez.
Midfielder and captain Pablo Pérez was instrumental in midfield and should have been on the score sheet in the first half.
Following a low driven free-kick, the ball fell kindly at the feet of the Boca captain whose shot just eluded the far post of Armani's goal.
With a minute remaining, the emotional Perez left the field of play to a roar from the Boca fans who evidently appreciated the hard work of their captain.
Esteban Andrada in the Boca goal almost cost his team a penalty if it wasn't for his slight play acting in the collision with River striker Pratto.
The goalkeeper came nowhere near to touching the ball as he took out the River striker but decided to stay down clutching his face - forcing the referee to award the free kick in his favour.
Both teams head back to their homeland of Argentina where Boca Juniors travel to Newell's Old Boys at the end of January and River host Patronato on January 27, looking to climb from their disappointing 11th position in Superliga.