The Eagles released a short statement on Tuesday confirming the parting of ways.
They didn't confirm whether Simpson would walk away immediately, or whether he would receive a farewell game.
Simpson was almost axed at the end of last year, and he knew the heat was on him again.
"We went through this last year, didn't we," Simpson said on the Seven Network on Monday night.
"We'll work through it. We'll keep the conversations pretty open.
"We'll keep moving forward. I'm sure we'll get a decision made."
Adam Simpson didn't have enough victories in recent seasons to stay in control at the Eagles. (Matt Turner/AAP PHOTOS)
Asked if he would like clarity on his position, Simpson replied: "I haven't really thought about that.
"I'm just trying to do my job as best as I can, and trying to explain what we're ... trying to get better at.
"I thought the early part of the season we had some really good results.
"There's a few games in the last month or so that have been pretty disappointing, so I can understand the rhetoric around it."
Simpson has been at the helm of West Coast since 2014, guiding the club to the 2015 grand final and the 2018 flag.
The Eagles have won just eight of their past 57 games, with the heat intensifying following lacklustre losses to Hawthorn and Melbourne over the past fortnight.
West Coast take on the Brisbane Lions at Optus Stadium on Sunday.
Star defender Jeremy McGovern is almost certain to miss the match with a fractured rib and a suspected punctured lung.
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