Two of Castillo's former ministers were also sentenced to 11.5 years in prison for the same crime. One of them is ex-Prime Minister Betssy Chávez, who was granted asylum by Mexico and remains inside the Mexican embassy in Peru´s capital, Lima.
The Peruvian government severed diplomatic relations with Mexico over the asylum to Chávez.
Castillo and his former ministers can appeal the decision.
This is the second Peruvian ex-president sentenced this week. A different court on Wednesday sentenced former leader Martín Vizcarra to 14 years in prison after finding him guilty of taking bribes while serving as governor of a southern state.
Castillo promised to be a champion of the poor when he took office in 2021, becoming the first president in the nation’s history to come from a poor farming community. He assumed the presidency without any political experience.
Castillo was replaced by his Vice President Dina Boluarte, who in October was also removed from office after a deeply unpopular government and amid a crime wave affecting the South American nation. The current president is José Jerí, who was the Congress leader.