The 83-year-old singer and his wife were attacked on November 30 by four unidentified robbers outside his villa in Diani, southeast of Nairobi, Kenya.
Di Stefano, who suffered severe head injuries trying to defend his wife, underwent two operations at a hospital in Mombasa and was later transferred to San Raffaele Hospital in Milan.
His wife was also hit in the head, and received 16 stitches at a local hospital.
The Sicilian-born di Stefano was considered on of the greatest voices of the 1960s and 1970s, and is well known for his duets with Maria Callas, with whom he also recorded many operas. He continued to perform until the 1990s.