Two other companies, Rail Cargo Austria and AWT, Czech Republic, also submitted offers, but according to local press reports only the Romanian bid met the conditions of the tender.
The total value of the transaction is expected to be around Kuna 1.1bn ($US 190m). HŽ Cargo carried around 12 million tonnes of freight, or 2.44 billion tonne-km, in 2011.
HŽ Cargo became a limited-liability company in 2007 as part of the restructuring of HŽ into a holding company, and until now has remained a wholly-owned subsidiary of HŽ Holding.
Last month the Romanian government announced it had chosen GFR as its preferred bidder for a 51% stake in national railfreight operator CFR Marfă.