The 1984–85 Yugoslav First Basketball League season was the 41st season of the Yugoslav First Basketball League, the highest professional basketball league in SFR Yugoslavia.

Teams placed fifth, sixth, seventh, eighth, ninth, and tenth were joined by the top two Second League teams for an 8-team play-in round.

The winner of each best-of-three series advanced to the playoffs quarterfinal round.

E- IB League east division champion W- IB League west division champion Borac Čačak-Sloga 116-91, 83-101, 118-100 Partizan-Rabotnički 110-89, 95-90 Budućnost-Jugoplastika 82-79, 89-101, 95-91 Šibenka-Olimpija 83-89, 77-87

Cibona-Borac Čačak 107-87, 108-85 Bosna-Partizan 91-84, 98-111, 97-98 Crvena zvezda-Budućnost 97-85, 79-95, 90-87 Zadar-Olimpija 111-86, 82-89, 100-97