The Catalans' campaign could not have got off to a better start, with the forward putting the seal on a scintillating team performance with a fine strike shortly after coming on
While Real Madrid stumbled to an 1-1 draw against Valencia earlier in the day, the Blaugrana's new boss picked up where predecessor Pep Guardiola left off, dominating their beleaguered Basque opponents from start to finish during an emphatic victory.
Carles Puyol headed Barca in front after four minutes, only for Gonzalo 'Chori' Castro to restore parity with an opportunistic finish moments later. But then Lionel Messi took over, scoring a pair of poacher's efforts in the 11th and 16th minutes to give the Catalans a lead they would never relinquish.
Pedro added the fourth just before half-time and Barca's perfect beginning to the season was completed by the return of David Villa from injury, with the Spain international marking his comeback with the home side's fifth and final goal, six minutes from the end.
Vilanova was not the only debutant for Barca, as Jordi Alba, the €14 million signing from Valencia, was handed a start at left-back. One of Sociedad’s new recruits, Castro, began up front, but fellow summer signings Carlos Vela and Jose Angel both had to settle for a place on the bench.
It took the Catalans only four minutes to break the deadlock, though the goal came, for them, in somewhat unconventional fashion, with a corner from Xavi being thumped in by the head of Puyol.
Sociedad were straight back down the pitch, with Castro coming within inches of connecting with a dangerous centre from Xabi Prieto at the far post. However, the ball did find its way to the former moments later - and he took full advantage.
Asier Illarramendi slipped a clever pass just in front of Dani Alves, putting Castro through on goal and he had the time to take a touch before burying his finish high into the roof of the net.
But just as Sociedad were able to hit back right after conceding, so too did Barcelona, who regained the lead within two minutes of the restart.
Messi’s uncharacteristically poor touch allowed a decent cross from Cristian Tello to get away from him, but Pedro worked the rebound back to the Argentine, who wriggled through his markers and slotted home.
Messi’s predatory instincts came to the fore again moments later, the forward reacting quickest to a Tello centre to drill the Blaugrana into a 3-1 lead, all after 16 minutes.
With a two-goal cushion, the hosts settled into their typical monopolisation of possession, suffocating Sociedad in their own half with large periods of metronomic passing.
A sublime combination between Messi and Cesc Fabregas carved the visitors apart, with only the legs of Claudio Bravo denying the Argentine his hat-trick.
Sociedad only threatened intermittently on the counter, but an audacious lob from the halfway line by Gorka Elustondo would force Victor Valdes into a safety-first palm over the bar.
However, Barcelona were always in control and with four minutes to go until half-time, they added a fourth in emphatic and enthralling fashion.
Messi, Xavi and Fabregas were all involved in a build-up that split Sociedad in two, with the ball worked wide to Tello, who centred to Pedro to stroke into the far corner.
Sociedad set up for a damage-limitation exercise in the second half, though Antoine Griezmann snatched at an early opening as he fired wide from a good position.
However, the focus was always at the other end of the pitch and an outstanding one-touch sequence between Messi and Pedro ended with the former blasting his finish into the side netting when he should have hit the target.
Xavi was next to try his luck, letting loose from 20 yards out with a strong arm from Bravo denying him a goal of his own.
The home fans were in jubilant spirits, which were kicked up a notch by the introduction of Villa for Pedro with a quarter of an hour to go, the Spain striker making his long-awaited return from the fractured tibia he suffered last December.
And Villa did not miss a beat, finishing a mazy run from Iniesta with aplomb in the 84th minute to round off a picture-perfect start to the new season for Barcelona, who will now go into their midweek Spanish Supercopa clash with great rivals Real Madrid brimming with belief.