Messi was again Barca's savior and his contribution helped produce a score which flatters a side that struggled especially in the first half to produce the fluid football that has characterized their game over recent seasons.
Barca's captain coolly converted a penalty to put the champions ahead in the 23rd minute but gave away a foul in a risky area which led to Lucas Olaza levelling for Celta with an outstanding strike from a free kick in the 42nd.
Messi restored Barca's lead right before halftime with a stunning free-kick of his own.
His first effort came just before the break, with the second - a near carbon copy of the first - coming at the start of the second half before Sergio Busquets put the seal on a 4-1 victory.
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Click through the gallery the players with the most hat-tricks in LaLiga history.
The Argentine superstar bagged two free-kicks and penalty to claim his 34th hat-trick in the Spanish top fight, equalling the record of Ronaldo's 34 hat-tricks.
On his way to his 34th hat-trick, Messi scored his 51st and 52nd free kicks which shows that he is also one of the best free-kickers in the world at the moment if not the best of the lot.
Valverde said: "It's impossible not to depend on Messi. Having him around gives us a real boost". "He dominates the art of free kick taking, and opponents know they can not afford to give away fouls near our area. The other day we had a painful defeat and we had to win today". If they do, we try to take advantage.