The 25-year-old does not feature in the first team picture at Loftus Road, and is expected to reunite with Celtic boss Brendan Rodgers.
Caulker has just one year left on his current contract, and Celtic have moved to land the former England defender on a cut-price deal.
Tottenham’s Harry Kane in action with QPR’s Steven Caulker
The defender joined QPR from Cardiff City in 2014, but has failed to make a strong impression at Loftus Road.
He has made just 50 appearances for the London club, and spent loan spells at Southampton and Liverpool.
Caulker recently admitted that he struggled with addictions to alcohol and gambling, and even considered committing suicide while going through the dark phase of his life.
Steven Caulker with Team GB
Rodgers admitted that he had spoken to Caulker and offered him help off the pitch. It now seems that the two clubs are trying to work out a deal.
Caulker previously worked with Rodgers during a season-long loan spell with Swansea City during the 2011-12 campaign.