Sky Sports News sources understand that Cahill is poised to finalise his departure from the Reebok Stadium amid speculation he was reconsidering the move to Stamford Bridge.
The Blues had already agreed a fee with the Trotters last month believed to be £7million but manager Andre Villas-Boas revealed two weeks ago that the club and player were 'miles apart' from agreeing personal terms.
Since then reports in the UK media suggested that Barclays Premier League champions Manchester United and Harry Redknapp's Tottenham Hotspur had launched last minute attempts to try and hijack the deal.
However, the 26-year-old now appears to have answered the call for Villas-Boas who is lacking options in defence after Brazil international Alex handed in a transfer request at the start of December.
Cahill is a key figure in Bolton's setup but his contract expires at the end of the season and Owen Coyle has opted to cash in on the player now rather than lose him for free at the end of the campaign.