The extremist group posted pictures of the two men wearing yellow prison outfits in the latest issue of its online magazine Dabiq. It identifies the Norwegian man as Ole Johan Grimsgaard-Ofstad, 48, from Oslo, and the Chinese man as Fan Jinghui, 50, a freelance consultant from Beijing.
The magazine lists a telegram number for "whoever would like to pay the ransom for his release and transfer."
It does not say when or where the two were captured. ISIS controls large parts of Iraq and Syria, and has killed several captives in gruesome videos released online.
Norwegian Prime Minister Erna Solberg, at a news conference in Oslo on Wednesday, confirmed that one of the hostages was a Norwegian man in his 40s being held in Syria and "everything indicates that (ISIS) is behind it."
Solberg said the man was captured at the end of January.
"The kidnappers have presented a series of demands and significant amounts of ransom money," she said. "We cannot give in and won't give in to pressure from terrorists and criminals. Norway does not pay ransom."
Despite the country's unwillingness to pay ransom, Solberg said Norwegian authorities are working with various parties in several countries to free the hostage.
"Our goal is to get our citizen home," she said. "But let me be very clear, this is a very demanding case."
Chinese officials could not immediately be reached for comment.