The 28-year-old returns to Italy, where he spent the first seven years of his professional career before joining Bristol City in 2017.
Djuric completed his move away from Ashton Gate on deadline day, joining the Serie B outfit ahead of the 2018-19 campaign.
"We wish Milan all the best for the future. He was a popular player here at Ashton Gate and we thank him for his service during his time here. I'm sure he'll be successful at Salernitana," Bristol City's chief executive officer Mark Ashton told the club's official website.
Djuric made 30 appearances for the Robins during his one-and-a-half-year stay, scoring five goals.