Cahill put the finishing touches to a reported five-and-a-half-year contract, having spent at least the previous fortnight wrangling over personal terms that threatened to scupper the deal.
But the England defender, then aged 26, suggested he had no intention of walking away from the lengthy negotiations between his representatives and Chelsea chief executive Ron Gourlay.
"Chelsea is a massive club, it is a club that looks to win trophies season in, season out and it is a big opportunity for me to be a part of that," he told the club's official website, www.chelseafc.com.
"Opportunities like this, you can't turn down."
There were no shortage of admirers for the defender, with Arsenal seeing a bid rejected the previous summer and Tottenham also going close to landing him.
But Chelsea were the only serious January transfer window bidders, with Bolton opting to cash in on a player who was in the final six months of his contract.
It proved to a be a shrewd move by Chelsea as Cahill went on to establish himself in the first-team and make almost 300 appearances for the club up until his release at the end of the 2017-18 season.
He helped the club win the Premier League and Europa League twice, while within months of his arrival they captured an elusive Champions League crown, with Cahill starting at the back alongside David Luiz in the final.