Real Sociedad have moved swiftly to replace sacked manager David Moyes by appointing Eusebio as his successor later that same day.
The Basque outfit relieved Moyes of his duties on Monday after a disappointing start to the La Liga season, where the team had won just two of their opening 11 games.
Friday's 2-0 loss at Las Palmas was the final straw for the Sociedad board and they finally took action in an effort to stop the rot after seeing La Real lose four of their last five league matches.
They have since turned to Eusebio, who has been out of a job since he was dismissed by Barcelona back in February, having been in charge of their B team for nearly four years.
The 51-year-old previously coached Celta Vigo when they were still in the Segunda Division, but has yet to oversee a club in the Spanish top flight.
Eusebio has two weeks to prepare his squad as Sociedad are only back in action after the international break with Sevilla visiting San Sebastian on November 21.
Commenting on his appointment, the Spaniard said: "I am proud and honoured to coach this club. It fills me with enthusiasm, the challenge of coming here to get to live beautiful moments.
"[The team] have all the conditions to grow and improve. Now [we] have to work and get that level of demand and commitment to change the dynamic and move forward."