The 22-year-old has joined Boro on a 93-day deal and is expected to go straight into the squad for Friday night’s home league game against Doncaster.
Ayala, who spent last season on loan at Nottingham Forest, began his career at Sevilla and was signed by then Liverpool manager Rafael Benitez in 2007.
The centre-half made five Barclays Premier League appearances for Liverpool and had loan spells with Hull and Derby before signing a four-year deal with Norwich in August 2011.
Ayala will team back up with former Norwich players Jacob Butterfield and Kei Kamara at Middlesbrough, who are searching for a new manager following the departure of Tony Mowbray on Monday.
Aberdeen boss Derek McInnes believes his side's form is being affected by a poor pitch at Pittodrie.