The 1965–66 Yugoslav Second League season was the 20th season of the Second Federal League (Serbo-Croatian: Druga savezna liga), the second level association football competition of SFR Yugoslavia, since its establishment in 1946.
A total of eighteen teams contested the league, including thirteen sides from the 1964–65 season and five sides promoted from the third tier leagues played in the 1964–65 season.
The five clubs promoted to the second level were Bosna, Leotar, Segesta, Slovan and Zadar.
At the winter break, Slovan abandoned competition due to lack of funding.
The four clubs promoted to the second level were Lovćen, Radnički Sombor, Sloboda Titovo Užice and Sloga Kraljevo.