The 56-year-old will not spend any time behind bars, though, as Spanish authorities tend not to enforce sentences of less than two years.
Mourinho appeared before a judge in a Madrid court to confirm the plea agreement he had reached with prosecutors.
The Portuguese tactician spent three years at the Santiago Bernabeu and won three titles for Los Blancos during his reign at the club, but failed to remit £2.9 million to the Spanish authorities.
The Portuguese will have to pay around £1.75m (€2m) in fines.
He was playing for Real Madrid at the time of the offence between 2010 and 2014 - the same team Mr Mourinho was managing at the time of his own tax violation.
Mourinho has been linked with a return to Real Madrid after reportedly turning down the Benfica job.
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Ronaldo received a two-year jail sentence immediately commuted to a fine of 365,000 euros and another penalty of 3.2 million euros, according to the sentence.
However, it's claimed by prosecutors that some of the information presented was incorrect.
In 2016, Mourinho's representatives Gestifute released a statement insisting he was "fully compliant with tax obligations" after allegations of tax evasion first came to light via the whistleblowing platform "Football Leaks".
Several other soccer figures have been subjected to investigations from tax authorities in Spain in recent years, including Lionel Messi, Javier Mascherano, Marcelo, Luka Modric, Alexis Sanchez, Ricardo Carvalho, Angel Di Maria, Radamel Falcao, Fabio Coentrao and Xabi Alonso.