A court statement on Wednesday said the sentence could be appealed through the Spanish supreme court.
Judges also sentenced the Argentine forward`s father, Jorge, to 21 months in prison for the same three crimes.
Under Spanish law a prison sentence of under two years can be served on probation, meaning Messi, 28, and his father are unlikely to go to jail.
The court also ordered Messi to pay a fine of around 2 million euro ($2.2m) and his father to pay 1.5 million euro ($1.6m) for the crimes.
Messi appeared in court in Barcelona in early June alongside his father to testify against charges of tax evasion.
"I was playing football. I had no idea about anything," Messi told the court at the time. "I trusted my dad and my lawyers."
Messi, the five-time FIFA World Player of the Year, has won four Champions League and eight Spanish La Liga titles with Barcelona.
Lionel Messi given 21-month sentence for tax fraud
06 July 2016
Read: 1349
Barcelona football star Lionel Messi has been sentenced to 21 months in prison after a Spanish court found him guilty of three counts of tax fraud.
