[3] Železničar won another title in 1940, this time in a knockout system, beating their rivals I. SSK Maribor 2–1 in the final.

They have defeated the West group winners Piran (6–0 and 1–2) for the unofficial title and thus qualified for the Croatian-Slovenian League.

They instantly returned to the Republic League in 1962 and renamed back to NK Železničar Maribor in the same year.

The results soon improved and the club won their third republic title in 1968–69, earning a place in the Yugoslav Second League for the first time in history.

They have won another republic title in 1972–73, but lost in the Yugoslav Second League (West) play-ofs against Mercator Ljubljana.

In 1981, despite scoring only fourth position, the Football Association of Yugoslavia offered them a place in the Yugoslav Second League, but the club declined promotion due to lack of funds.

[3] They have immediately finished first and earned a promotion to the first division in the 1991–92 season, managed by their former player Jože Karmel.