“It’s obviously re-assuring to have the endorsement from the board that they support the direction we are taking,” Simpson told the club website.
“We have been in constant dialogue in recent months and I am really pleased to have the opportunity over the next four years to continue to build on what we have started.
“We have transitioned our squad over the last 12-18 months and I am excited about the next phase of our progression.
“I have been extremely grateful for everything the club has done for my family and I since the day we arrived.
“We have not reached the ultimate target at this point, but we are focused on creating opportunities and an era of sustained success.”
Adam has done a terrific job in his five years as senior coach,” Nisbett said.
“He has overseen the transition of our squad, with a number of outstanding players over the last few years, particularly the last 12 months.
“He has laid a strong platform for the next era at our club and we look forward to him building on those foundations.”
Simpsons surged the Eagles to second spot on the ladder this season, and they will clash with Collingwood in a qualifying final Saturday week.