Europe hold the Ryder Cup and Poulter has four times been on the winning side in five editions, including the most recent at Scotland's Gleneagles course in 2014.
Although he has never won one of golf's four major championships -- the US Open, British Open, US Masters and US PGA -- Poulter has a superb Ryder Cup record.
Of all European players who have appeared in at least 15 ties, none has a better winning percentage than Poulter's 72.2.
"Everyone who knows me knows how much the Ryder Cup means, having given me memories to savour over the past 12 years and created friendships that will last a lifetime," said Poulter in a statement issued Monday.
"Therefore when it became clear, given my current foot condition, that I would not be in a position to try and qualify for the team for a sixth time this year or indeed be able to justify a wild-card pick, I was truly honoured and delighted to be asked by Darren to be a vice-captain.
Poulter sparked visitors' Europe's so-called 'Miracle at Medinah' in 2012, with five straight birdies to partner Rory McIlroy to victory in the Saturday afternoon fourballs against the United States' Jason Dufner and Zach Johnson.
Northern Ireland's Clarke, who was Poulter's partner in the latter's first Ryder Cup match in 2004, said: "I am absolutely delighted to name Ian as my fourth vice-captain for the match at Hazeltine.
"Ian's Ryder Cup record speaks for itself and stands comparison with anyone in the history of this great contest. It goes without saying what a vital presence he will be in our team room come September.