Europa League winners Sevilla surprised the Champions League holders when Ever Banega netted a delightful free-kick.
Lionel Messi scored two sublime free-kicks to put Barca 2-1 ahead before Rafinha and Luis Suarez made it 4-1.
Jose Antonio Reyes, a Kevin Gameiro penalty and a Yevhen Konoplyanka goal forced extra time before Pedro struck.
Barcelona’s first success in the competition since 2011 means they join Italian side AC Milan in winning it five times.
- Re-live Barcelona’s dramatic Super Cup victory over Sevilla
The good, the bad and the ugly
Barca coach Luis Enrique and his players celebrated wildly when Scottish referee Willie Collum blew the final whistle after 01:00 local time.
But the Catalans provided La Liga rivals Real Madrid with much optimism as Rafael Benitez prepares for his first season in charge at the Bernabeu.
Having coasted into a 4-1 lead – with Messi’s two sumptuous curling free-kicks the pick of the four goals – Barca capitulated, conceding three times in 24 minutes.
Enrique’s side scored 110 goals as they won La Liga last season, and they may have to find just as many if they are to successfully defend the title after their defensive frailties allowed Sevilla back into a game they should have been out of.
Yet Barca’s triumph means they have now won four trophies this year after winning the treble last season.
They remain on course to emulate the record-breaking feat of Pep Guardiola’s side in 2009 when they won all six trophies available to them.
Barca can secure a fifth trophy of the calendar year when they face Athletic Bilbao in the two-legged Spanish Super Cup, the first leg on Friday with the return at the Nou Camp next Monday.
As European champions, they will also compete in the 2015 Fifa Club World Cup in Japan in December.
Match-winner Pedro has told Barcelona he wants to leave the European champions, according to technical secretary Robert Fernandez.
Manchester United have been heavily linked with a move for the Spain international as they look to replace Angel Di Maria, who joined Paris St-Germain for £44.3m last week.
And having won five league titles and the Champions League three times with Barca, Pedro’s days at the Nou Camp appear to be drawing to a close.
If this was his farewell appearance it barely could have been more dramatic, the 28-year-old pouncing on the rebound after Sevilla keeper Beto had denied Messi a hat-trick of free-kick goals.
Enrique opted to leave the long-serving winger on the bench and start with Rafinha, and it was not until extra time that Pedro was sent on.
‘We feel frustrated despite winning’
Barcelona defender Javier Mascherano: “For the fans it was a great spectacle and something rarely seen. Aside from the win though we feel frustrated as we had gone ahead and were in control but let it slip.
“I am happy with the win but there is a lot to improve on.”
Barcelona match-winner Pedro: “I got the goal but it was down to the work of the team and I am happy with the win.”
Man of the match
The stats you need to know
- Pedro has scored two European Super Cup goals, both in extra-time, both in the 115th minute and both winners.
- Sevilla are the only team to have scored four goals in a game against Barcelona with Luis Enrique as manager.
- Luis Suarez has scored or assisted in his three finals for Barcelona.
- Lionel Messi has scored two direct free-kick goals in the same game for the first time in his career.
- Messi has scored 10 goals in his last six games against Sevilla.
Lineup, Bookings (9) & Substitutions (6)
- 01 ter Stegen
- 06 Dani Alves Booked
- 03 Piqué
- 14 Mascherano (Pedro – 93′ Booked )
- 24 Mathieu Booked
- 04 Rakitic
- 05 Busquets Booked
- 08 Iniesta (Sergi – 63′ )
- 10 Messi
- 09 Suárez
- 12 Rafinha (Bartra – 78′ )
- 07 Pedro
- 13 Bravo
- 15 Bartra
- 20 Sergi
- 21 Adriano
- 29 Ramírez
- 31 El Haddadi
- 13 Beto
- 23 Andújar Moreno Booked
- 03 Rami
- 04 Krychowiak Booked
- 02 Trémoulinas
- 07 Krohn-Dehli Booked
- 19 Banega Booked
- 10 Reyes (Konoplyanka – 68′ )
- 08 Iborra (Ferreira Filho – 80′ )
- 20 Machín Pérez
- 09 Gameiro (Immobile – 80′ Booked )
- 01 Rico González
- 11 Immobile
- 12 Kakuta
- 16 Sánchez Benítez
- 17 Suárez
- 22 Konoplyanka
- 25 Ferreira Filho
Live Text Commentary
Full Time Match ends, Barcelona 5, FC Sevilla 4.
Second Half Extra Time ends, Barcelona 5, FC Sevilla 4.
120:00 +1:13 Attempt missed. Adil Rami (FC Sevilla) left footed shot from the left side of the six yard box is close, but misses to the left. Assisted by Ciro Immobile following a set piece situation.
120:00 +0:55 Foul by Luis Suárez (Barcelona).
120:00 +0:55 Mariano (FC Sevilla) wins a free kick on the right wing.
Booking Dani Alves (Barcelona) is shown the yellow card.
Booking Michael Krohn-Dehli (FC Sevilla) is shown the yellow card.
118:25Dani Alves (Barcelona) wins a free kick on the right wing.
118:25Foul by Michael Krohn-Dehli (FC Sevilla).
117:16Attempt missed. Coke (FC Sevilla) header from the centre of the box is close, but misses to the left. Assisted by Éver Banega following a set piece situation.
Booking Sergio Busquets (Barcelona) is shown the yellow card for a bad foul.
116:24Foul by Sergio Busquets (Barcelona).
116:24Yevhen Konoplyanka (FC Sevilla) wins a free kick in the attacking half.
114:07 Goal scored
Goal! Goal! Barcelona 5, FC Sevilla 4. Pedro (Barcelona) left footed shot from the left side of the six yard box to the top left corner following a set piece situation.
114:05Attempt saved. Lionel Messi (Barcelona) left footed shot from outside the box is saved in the bottom left corner.
114:03Attempt blocked. Lionel Messi (Barcelona) left footed shot from outside the box is blocked.
112:52Lionel Messi (Barcelona) wins a free kick in the attacking half.
112:52Foul by Mariano (FC Sevilla).
110:21Corner, Barcelona. Conceded by Coke.
109:49Lionel Messi (Barcelona) wins a free kick on the right wing.