Simpson said he was looking forward to the opportunity of coaching in his own right.
“I am grateful for this opportunity and I look forward to moving across to Perth with my family and settling in to the challenge ahead,” he said.
“I have always admired West Coast from afar and I believe the list has an exciting mix of senior and emerging young players.
“I would like to acknowledge both Hawthorn and North Melbourne for the grounding they have given to me in this game.
“Hawthorn has been fantastic for me in the last four years and it was certainly a great experience to be a part of the coaching group as the club achieved the ultimate success last Saturday.
“In particular, I’d like to thank Alastair Clarkson and Chris Fagan for the wonderful education and assistance that they have provided to me.
“Being so closely involved from a coaching perspective has provided me with a sense of the hard work which has to be done to achieve a premiership. I obviously enjoyed that feeling as a player, but it is different as a coach.
“I will move across to Perth as soon as possible and I look forward to meeting the players and working with them from the start of pre-season.”
Eagles ruckman Nic Naitanui Tweeted on Thursday evening: "Welcome on board Adam Simpson," then followed a few minutes later with: "And yes I got the text this time haha" in reference to his late notice of Worsfold's leaving.
The original pool of 14 candidates had been whittled down this week, with the Eagles forced to wait for the Dockers and Hawks to finish their campaigns before formal interviews started.
It is understood highly rated assistant Scott Burns was told earlier in the week he was no longer in the running, with a decision left between the final two.
In the spirit of reconciliation the AFL acknowledges the Traditional Custodians of country throughout Australia and their connections to land, sea and community. We pay our respect to their Elders past and present and extend that respect to all Aboriginal and Torres Strait Islander peoples today.