The 24-year-old Western Australian explained the chance for his family to come and see him play regularly was a major factor in his decision to leave the Magpies.
Having nominated his preferred trade destination, Wellingham has an overseas trip planned and will leave West Coast and Collingwood to sort out a deal.
"I spent the last week working through the decision and the process with my manager and I am really looking forward to continuing my career at West Coast," Wellingham told Triple M in Melbourne.
"I am very appreciative of the opportunities that Collingwood gave me, I will always have some very good friends there but it is now time to move on.
"The dealings I have had with West Coast have been really impressive and I will now go on a break overseas and wait for the two clubs to reach a deal on the terms of my move back home.
"It will be exciting to get back to Perth and to play in front of my family every week.
"That was a very strong influence on my decision to leave and I look forward to playing with the Eagles."
Wellingham has played 92 games for Collingwood since being drafted by the Magpies with pick 10 in the 2006 AFL Rookie Draft.
The speedy midfielder has played 20 or more games for the Magpies in each of the past three seasons.
Wellingham believes joining the Eagles could mean an opportunity to win a premiership, something he achieved with Collingwood in 2010."Playing against them, we had enormous respect for West Coast, and I believe they have a young list capable of winning a premiership in the next few years," Wellingham said.