The Serie A champions beat Barca by the same scoreline in the quarter-finals last season before holding out for a second-leg stalemate at Camp Nou.
Barca have since lost Neymar to Paris Saint-Germain, but it was Juve's' most notable pre-season departure – Leonardo Bonucci's surprise switch to AC Milan – that loomed largest over this match as a once formidable defence was cut to ribbons in Giorgio Chiellini's injury absence.
Record signing Ousmane Dembele was busy on his full Barca debut, but it was a more familiar face that thrilled the home crowd.
Messi's magnificent opener in the final minute of the opening 45 marked the first time he has scored against fellow all-time great Gianluigi Buffon in the Juventus goal.
After making the second for Ivan Rakitic he repeated the trick to seal the points and maintain Barca's resurgent early season form under Ernesto Valverde.
Juve right-back Mattia De Sciglio joined Dembele in making a full debut for his new club and was almost the surprise source of the first goal in the sixth minute – Barca goalkeeper Marc-Andre ter Stegen managing to tip wide as a speculative left-footed strike angled awkwardly away from him.
Messi botched an attempt to slide a free-kick under the wall and, precision having failed, Luis Suarez went for power on the rebound, forcing an unsighted Buffon to push over at full stretch.
Last-ditch challenges from Gerard Pique and Alex Sandro at either end took the sting out of attempts from Paulo Dybala and Dembele.
Alex Sandro's intervention was required following a slack pass from De Sciglio – his last contribution before hobbling off through injury – and Messi pounced as the Juve reshuffle fell into place.
Collecting the ball from Dembele on halfway, Barca's talisman drove at the visitors' backline and, having shaped to play in Jordi Alba, slipped the ball to Suarez.
The Uruguayan's deft lay-off was gladly accepted by Messi, who arrowed a shot through Medhi Benatia's legs and into the bottom-right corner.
Dybala fired wastefully off target when Pique failed to deal with Alex Sandro's cross early in the second half, while his dazzling compatriot Messi struck the post from the edge of the box at the other end – Buffon a relieved onlooker as the rebound spun off his shoulder to safety.
Messi blotted a fine evening's work in the 55th minute when he signalled to referee Damir Skomina with an imaginary yellow card for Miralem Pjanic. The upshot was a flash of the real thing, with Camp Nou jeering and whistling in support of their hero.
The five-time Ballon d'Or winner was back to what he does best soon enough – tearing into space behind Alex Sandro on the Juventus left. Messi's attempt was hacked out of the goalmouth by Stefano Sturaro, but only as far as Rakitic, who converted left-footed.
Suarez side-footed over from an Alba cross before Messi continued to torment increasingly bedraggled foes.
Andres Iniesta served as the familiar and ever-reliable supply line and, as Dembele's run across the Juve defence added to their confusion, Messi scooted inside Alex Sandro and smashed past a helpless Buffon.
Suarez had a fourth disallowed, the linesman's flag sparing a Buffon fumble, while Juve's cries for handball against Pique fell on deaf ears when he cleared Benatia's header off the line. It summed up a fruitless endeavour for Massimiliano Allegri's men.
Key Opta facts:
- The last time Juventus conceded at least three goal in a Champions League match at the group stage was in December 2009, against Bayern Munchen.
- Eight of the last nine goals Juventus conceded in the Champions League were scored by Spanish teams (Sevilla, Real Madrid, Barcelona).
- The Bianconeri have failed to score only in two of their last 13 Champions League matches, both times at the Camp Nou against Barcelona.
- Barcelona are unbeaten in their last 12 home games against Italian sides in European competitions (W9 D3).
- Lionel Messi scored his first Champions League goals against Gianluigi Buffon: the Argentinian found the back of the net with his first touch in opposition box.