Sevilla president Jose Castro voiced objections over the Spanish season's curtain-raiser being taken away from its traditional two-legged format to be played in Morocco but Pablo Machin's side started the brighter.
Pablo Sarabia followed his three goals in the Europa League preliminary stages with a ninth-minute opener that was cancelled out by Gerard Pique three minutes from half-time.
Dembele put the injury misery that ruined his debut season in Catalonia behind him by blasting in a rasping right-footed strike via the crossbar, although there was a final twist
Ter Stegen brought down ex-Barca full-back Aleix Vidal, only to atone for his clumsiness by holding a tame spot-kick from Sevilla substitute Wissam Ben Yedder.
Sarabia was forced to put his celebrations on hold after collecting Luis Muriel's pass and drilling a low shot past Ter Stegen but, after reviewing his linesman's incorrect offside call, referee Carlos del Cerro Grande allowed the goal to stand.
Sevilla goalkeeper Tomas Vaclik denied Lionel Messi and Jordi Alba before Clement Lenglet headed over from a Messi free-kick against his former employers.
Luis Suarez dragged a glorious chance wide but Barca were level when Messi's free-kick spun off the post and the unfortunate Vaclik for Pique to prod home.
Sarabia almost instantly restored Sevilla's advantage, only for Ter Stegen to stand firm following more fine work from Muriel.
Franco Vazquez glanced against the top of the Barcelona bar from an Ever Baenga corner and clipped a shot agonisingly wide from the Argentina playmaker's pass in the 69th minute.
Vaclik thwarted Messi and Suarez with a brilliant double save but he had no chance when Dembele dazzlingly tried his luck with 12 minutes to play. Ben Yedder would gallingly fail with his considerably easier chance.
What it means:
Messi is now the most decorated player in Barcelona history with 33 honours to his name. It puts him out in front ahead of Andres Iniesta. The period of adjustment without the master playmaker will take time, but a piece of silverware certainly helps.
Pat on the back: Dembele enjoys moment to remember
Lumbered with a huge price tag in the aftermath of last year's Neymar madness, Dembele suffered rotten luck with injuries and Malcom's arrival prompted speculation around his future. The France international producing such a sublime strike seems a decent way to ensure head coach Ernesto Valverde keeps him around.
Boot up the backside: Exit looms as Rafinha fails to impress
Philippe Coutinho, Ivan Rakitic and new arrival Arturo Vidal being stationed on the Barca bench gave Rafinha a chance to press his case. The midfielder failed to do so – tidy in his passing without truly impacting upon the action – and made way for Rakitic at the break. Another move elsewhere for the 25-year-old, who spent the second half of last season on loan at Inter, can be expected to follow.
Boca Juniors are Barcelona's guests in the Joan Gamper Trophy before Valverde's men start their LaLiga defence at home to Alaves. Sevilla travel to Zalgiris with a 1-0 Europa League advantage and open up domestically at newly promoted Rayo Vallecano.
Key Opta stats:
- Barcelona have won the Supercopa 13 times, more than any other team in the history of the competition.
- Barca have appeared in the Supercopa in nine of the last 10 seasons, winning the title six times (2009, 2010, 2011, 2013, 2016 and 2018).
- This has been the Sevilla's fourth appearance in the Supercopa. The Andalusians won the title in their first appearance versus Real Madrid in 2007 and have also lost three all against Barça (2010, 2016 and 2018).
- Marc-Andre ter Stegen has conceded his second penalty for Barcelona in all competitions. The German goalkeeper has saved four of the 11 penalties he has faced for the Catalonian club.
- Pablo Sarabia has scored 11 goals in 2018 in all competitions, more than any other Sevilla player.