The Barcelona court found both the soccer star and his father, Jorge Horacio Messi, guilty of three counts of defrauding the tax department to the tune of €4.1m.
In Spain, sentences of less than two years for first offences are suspended, meaning neither man will go to jail.
The court also fined Messi €2m and his father €1.5m.
During the four-day trial last month, Messi and his father denied any wrongdoing.
Both said the player was unaware of the tax issues that led to the fraud charges.
However, the state prosecutor argued that Messi and his father failed to prove their innocence and were unable to show that the player did not have at least some knowledge of the corporate structures created to lower his tax burden in Spain.
Tax inspectors said they found evidence that Messi’s father used companies in countries such as Uruguay, Switzerland, and Belize to reduce tax on the player’s income from image rights.
Messi’s father said he was told by a legal adviser that the practice was legal.
The sentence can be appealed against.
Barcelona issued a statement in Catalan to “express its complete support for Leo Messi and his father”.
“FC Barcelona remains at the disposition of Leo Messi and his family to stand by him in any actions that he decides to take in defence of his honour and legitimate self-interests,” it said.
The 29-year-old Messi is Argentina’s career-leading scorer with 55 goals in 113 international appearances. However, he has lost three Copa America finals with Argentina (2007, 2015, and 2016) and announced his international retirement after last month’s penalty shootout loss to Chile.
With Barcelona, however, Messi has won four Champions League titles and three Club World Cup trophies.
He also won eight Spanish league titles, scoring 453 competitive goals in 531 games, including a league-record 312.
This is just one legal case involving Barcelona’s players.
Earlier this year, Javier Mascherano was handed a suspended one-year prison sentence for not paying all his taxes for 2011 and 2012.
Adriano is also being investigated for alleged tax fraud, while Neymar has had to testify before a judge because of alleged irregularities involving his transfer to Barcelona.
He and the club are accused of withholding the real amount of the transfer fee, in part to avoid paying the full amount of taxes.
They have denied wrongdoing.