The league was contested in two regional groups (North Division and South Division), with 12 clubs each.
Cibalia and Novalja, winners of the North and South Division, qualified for a two-legged promotion play-off, which took place on 24 and 28 May 2005.
Cibalia won the tie 5–1 on aggregate score, thereby earning promotion to the Prva HNL for the following season.
However, Novalja had another chance for promotion, as the losing team from the promotion play-off played another two-legged tie against the 11th placed team of Prva HNL, Međimurje.
Međimurje won 3–1 on aggregate.