La Liga leaders Barcelona thought that they had made the breakthrough in the 13th minute of the contest through Robert Lewandowski, who netted from inside the box after a blocked shot from Frenkie de Jong, but the closest of offside calls, following a VAR check, denied the division leaders.
The Catalan outfit were without the services of Lamine Yamal due to an ankle problem, but they did manage to recover Pau Cubarsi despite the centre-back suffering a horror facial injury against Red Star Belgrade in the Champions League last time out.
Real Sociedad managed to make the breakthrough in the 33rd minute of the match, and it was a disappointing goal from Barcelona's point of view, as Luka Sucic's header was allowed to drift through to Becker, who expertly picked out the bottom corner.
Barcelona had seven shots in the first period, but none of those were on target, with the hosts proving to be the more productive outfit in the final third, with Yamal certainly being missed by Hansi Flick's side.
The hosts had a big chance to make it 2-0 early in the second period, but Mikel Oyarzabal saw his effort saved by Barcelona goalkeeper Inaki Pena.
In the end, though, one goal proved to be enough for Real Sociedad, with Barcelona incredibly not managing to register a single shot on target during Sunday's affair, with their winning run coming to an end in incredibly disappointing fashion.
Barcelona remain top of the La Liga table, six points clear of second-placed Real Madrid, who have a game in hand, while Real Sociedad have risen into eighth, now boasting 18 points from their opening 13 matches of the season.
REAL SOCIEDAD VS. BARCELONA HIGHLIGHTS
Sheraldo Becker goal vs. Barcelona (33rd min, Real Sociedad 1-0 Barcelona)
Real Sociedad make the breakthrough in the 33rd minute of the contest, and the goal comes from Becker, who breaks onto a loose ball inside the Barcelona box before expertly picking out the bottom corner of the net.
Not too sure about the defending from the division leaders there!
MAN OF THE MATCH - IGOR ZUBELDIA
There were a lot more glamorous names on the field on Sunday night, but Zubeldia was the match's outstanding player, with the 27-year-old putting in an excellent performance for Real Sociedad in the middle of their defence.
Zubeldia won two aerial duels and made two tackles during his 90 minutes on the field, while he completed 54 of his 61 passes during an outstanding defensive performance, with Barcelona's forwards struggling to get the better of him.
REAL SOCIEDAD VS. BARCELONA MATCH STATS
Possession: Real Sociedad 30%-70% Barcelona
Shots: Real Sociedad 14-11 Barcelona
Shots on target: Real Sociedad 6-0 Barcelona
Corners: Real Sociedad 7-6 Barcelona
Fouls: Real Sociedad 17-6 Barcelona
BEST STAT
WHAT NEXT?
Barcelona will be aiming to bounce back from the shock defeat when they head to Celta Vigo in La Liga on November 23, before welcoming Brest in the Champions League three days later.
Real Sociedad, meanwhile, will be bidding to use the result to kickstart their campaign, and Imanol Alguacil's side will return to league action against Athletic Bilbao in the Basque derby on November 24.