The hosts recently parted ways with Gaizko Garitano and appointed former Valencia manager Marcelino in his stead. However, the 55-year-old's first match in charge did not go according to plan.
In what was a perfect start for Athletic Bilbao, ever-present forward Inaki Williams broke through on a counter-attack and placed a sumptuous finish beneath the grasp of Marc-Andre ter Stegen.
Another quick break three minutes later saw the hosts fashion another chance but Yuri Berchiche could only direct his shot to the side net, leaving an unprotected Ter Stegen furious at his defence.
The opening minutes saw breathtaking action at both ends. Barcelona fashioned their first chance of the game when Lionel Messi and Antoine Griezmann combined brilliantly to set Sergino Dest up. However, the right-back could only shoot straight at Unai Simon.
This seemed to lift the Blaugrana's spirit, and they slowly began to exert their dominance in the game, with a well-deserved equaliser coming in the 14th minute.
A 35-yard cross-field ball by Messi found Frenkie de Jong at the far-post. The Netherlands international showed great technique to square the ball back into the area for Pedri to head into an empty net.
Unai Simon was, however, at fault for the goal, having misjudged the flight of the ball to leave him trapped in no-man's land.
The Spain international was again to blame for Barcelona's second, as he rushed out to challenge Pedri, thinking he would shoot, only for the 18-year-old to set Messi up with a clever back-heeled pass.
Athletic Bilbao came out the stronger of the two sides after the break but the visitors carried all the punch in attack and fashioned several good chances before finally getting a deserved third.
Antoine Griezmann did well to find Messi in the area. The Argentina international rattled home with a one-time finish via the underside of the crossbar to put Barcelona 3-1 up.
More chances fell the way of Antoine Griezmann and Ousmane Dembele but neither failed to take them. Although a late goal by Iker Munian in the 90th minute threatened a grandstand finish, Barcelona ultimately held on for the victory.
Here, we shall highlight five talking points from the fixture.
#5 Poor run of form continues for Athletic Bilbao
Athletic Bilbao came into this clash having picked up just two wins from their previous eight La Liga games, with those victories coming in games against two newly-promoted teams.
The Basque outfit have struggled to match expectations, considering the talent in the side. It was on the back of this poor run that they decided to part ways with Garitano.
His replacement Marcelino seemingly had the perfect start when Barcelona conceded inside three minutes. However, the Catalans rallied to condemn Los Leones to their fifth defeat from just nine home games.
The defeat leaves Athletic Bilbao sitting in 9th on the table. Depending on how results go elsewhere, they could find themselves as low as 14th at the conclusion of this gameweek.
#4 Morale-boosting victory for Barcelona
This has been one of the most testing campaigns in the history of Barcelona, as off-field and on-field issues have combined to ensure the club have struggled to match previous standards.
However, results have improved in recent weeks, and this victory against Athletic Bilbao means that the Catalans are now unbeaten in seven La Liga games.
The win also moves Barcelona up to third on the table. Although they are still some way off the capital clubs, the fact that they picked up three points against one of the traditional sides in the league on a difficult ground would boost confidence within the camp.
Most pleasing for Ronald Koeman would have been the way his side rallied from their early deficit, indicative of a strong character, while they also dominated proceedings for most of the game.
Despite not getting on the scoresheet, Griezmann had one of his better games in a while and ended the game with an assist. His overall play was also devoid of the hesitancy that has weighed him down in recent weeks.
In total, Barcelona registered 15 shots in the game, with nine of those on target, and they proved to be good value for the victory at San Mames.
The only negative was the fact that two goals were conceded, with Barcelona's ridiculously highline early in the game punished to the maximum by the hosts.
Nevertheless, the club would be buoyed by this morale-boosting victory and will now focus on building momentum, starting from this weekend's trip to Granada.