After a protracted trial that enthralled and sickened the Spanish public, the nine-member jury found Breton guilty of murdering his children, Ruth, aged 6, and José, aged 2.
Bretón had originally told police that he lost the two children in a park.
But the jury found he had first drugged the children — either to send them to sleep, or to kill them — before burning their bodies in a bonfire 'kiln' oven on his parents' property.
The unanimous verdict of the jury came after over three days of deliberation.
It was announced in a jury statement read out on Friday in the provincial court of Cordoba, Spain.
Breton remained calm while the jury gave answers to 22 questions posed by the court. Jurors were unanimous on all points.
The lawyer for the prosecution in the case, María Ángeles Rojas Delgado, is seeking a sentence of 40 years for Breton.
Sentencing is expected to follow.