The Spanish court handed the same sentence to the Argentine player's father, Jorge Horacio, with a 1.5 million euro fine. Both defendants said they would appeal to the supreme court.
"The sentence is not correct and we are confident the appeal will show the defence was right," Messi's lawyers said in a statement. They added Messi had always acted in good faith.
Spanish law is such that any sentence under two years for a non-violent crime rarely requires a defendant without previous convictions to serve jail time.
A spokeswoman for the court confirmed that Messi, 29, was unlikely to be imprisoned.
Messi, five times World Player of the Year and one of the world's highest-earning athletes with an estimated income of $350 million in the past 10 years, plays for Barcelona football club where he is the leading goal scorer of all time.
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The court in Barcelona said in a ruling that Messi and his father defrauded the Spanish tax office of almost 4.2 million euros between 2007 and 2009 by using a web of shell companies to evade taxes on income from the player's image rights.
The companies - with names such as Sport Consultants and Sport Enterprises - were based in countries such as Belize, Uruguay, Switzerland and Britain where legislation kept the identities of their owners secret, it said.
Messi admitted during the trial in early June to signing contracts protecting his image rights but said he had no knowledge he was committing any wrongdoing or defrauding the Spanish state.
He said his father had control over his financial affairs, but the court said on Wednesday that this was not enough to avoid charges and Messi's "ignorance" did not remove responsibility.
"The information that the accused avoided having was, in reality, within his reach via trustworthy and accessible sources," the presiding judge, Mercedes Armas Galve, wrote in the ruling.
Barcelona's top goal scorer
Messi, who has held Spanish nationality since 2005, and his father already had paid 5 million euros to the tax authorities as a "corrective" measure after formal investigations were opened.
Jorge Horacio Messi said during the trial that he was acting on advice from advisers who told him the practice was legal.
Barcelona football club said in a statement following the ruling that it not consider the player to be in any way criminally responsible.
"FC Barcelona continues to be at the disposal of Leo Messi and his family to support him in whatever action he decides to take in defence of his honesty and his legal interests," the club said.
Messi, who has won eight La Liga titles, four King's Cups and four Champions League crowns with Barcelona, said last month he was quitting international soccer after the Argentine national side, of which he was captain, lost on penalties to Chile in the Copa America tournament.
His estimated income of $350 million in the past decade makes him 10th on Forbes Magazine's list of the world's highest-earning athletes.
The sentence is not the first time Barcelona's players have become tangled in tax evasion scandals.
In January, fellow Barcelona player Javier Mascherano accepted a one-year prison sentence for defrauding authorities of over 1.5 million euros as part of a plea bargain, and also avoided jail time. Like Messi, he also pinned the blame on those who had advised him on his personal finances.
