The 56-year-old is accused of committing tax fraud in 2011 and 2012 when he coached Spanish giants Real Madrid.
The Portuguese will not spend any time in prison as the sentence is for less than two years.
Mourinho acknowledged the offences before the court in Madrid in a hearing which lasted just a few minutes.
The former Chelsea and Inter Milan boss has been commanded to pay a fine of more than €3 million.
In January, Cristiano Ronaldo accepted a fine of €18.8m and a suspended 23-month jail sentence, in a case which was also centred around tax owed on image rights.
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The 45-year-old Norwegian football manager replaced Mourinho could soon be made permanent if he continues his unbeaten run since taking charge.
Spanish tax authorities claimed Mourinho owed £3m - he had already settled a previous claim relating to his Spanish taxes after a 2014 inquiry, which resulted in a penalty of £1.1m.
Image rights cover the use of a person's likeness, voice, signature and mannerisms - and can be very lucrative for footballers and managers.
Mourinho had appeared before a judge in 2017 and denied any wrongdoing, saying he had paid everything he owed to Spanish tax authorities from the time he coached Real Madrid.
Prosecutors claimed he did this to obscure the extent of his financial gain from image rights deals and that he failed to declare such earnings while working in Spain.