The Eagles say he would have been offered a new contract regardless, given the positive impact the 26-year-old has made on the club in his first season since crossing from Hawthorn as a free agent.
Ellis injured his shoulder against Collingwood in round 20 but had performed well in his 17 games with the Eagles up until that point.
"It feels like he has played [at the club] for his entire career," football operations general manager Craig Vozzo told AFL.com.au.
"Irrespective of the trigger he would have been offered a contract.
"We are delighted with having him at our club and look forward to what he will bring moving forward."
Ellis was selection No.3 in the 2005 NAB AFL Draft and played 86 games with the Hawks.
He was a key player in the 2008 premiership team, and then battled with injuries and opportunity between 2011 and 2013, but he played in the 2012 Grand Final.
Ellis joined the Eagles as a free agent on a performance-based contract with Eagles' coach Adam Simpson, who had been an assistant at Hawthorn, keen to have him on board.
Ellis has played mainly in defence this season, using his skills to set up play, but has managed to kick seven goals when drifting forward.
