The club's website said Spaniard Macia, 42, would begin the job with immediate effect.
Macia previously worked with Leicester manager Claudio Ranieri in La Liga at Valencia.
"Eduardo's appointment follows an extensive process undertaken by the football club," Leicester's Director of Football Jon Rudkin said in a statement.
"His expertise and network of contacts will add considerable strength to our existing team of recruitment staff, whose skill and diligence contributed greatly to a successful summer transfer window."
Macia has also worked with Greek champions Olympiakos, Spanish side Real Betis and Italian club Fiorentina.
Walsh's departure to Everton as director of football was a blow to Leicester as he was the man responsible for bringing the likes of N'Golo Kante and Riyad Mahrez to the club.
(Reporting by Martyn Herman; editing by Amlan Chakraborty)
