The 20-year-old arrived in south Wales with a lofty reputation last summer, but is set to return to his former club after failing to make his mark in the Premier League
The striker only left Denmark for Wales in June, but has struggled to break into the Cardiff side and his eight Premier League appearances so far have all come from the substitutes bench.
Cornelius arrived for a then club-record fee believed to be in the region of £8 million, but he has been hampered by an ankle injury for much of the campaign.
New Bluebirds manager Ole Gunnar Solskjaer has brought in Jo Inge Berget and Kenwyne Jones this month, increasing competition for places up front.
"FC Copenhagen can announce that the club is close to closing a deal with Andreas Cornelius. More to follow in the coming days," a statement on the club's Twitter feed read.
Cornelius has started in both of Cardiff's FA Cup ties during January without finding the net.
The Danish Superliga side are third in the table after 18 games, six points behind leaders Midtjylland and three behind Aalborg.