Mickelson won the title, thanks to a typically magical chip on the first extra hole of a play-off against Branden Grace.
Mickelson will attempt to lift the Claret Jug for the first time, when he tees up at Muirfield next week.
Mickelson, famed for his short game prowess, and a four-time Major winner, showed exactly why after making light of a bare lie to stop his wedge shot on the par-five 18th hole within a matter of inches of the cup.
Having tapped in for birdie, Mickelson watched on as Grace's valiant attempt to follow him in from 30 feet drifted past the hole, thereby handing the American the win and, with it, a cheque for 579,079 euro.
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It was a dramatic finish. Grace, the South African, set the clubhouse target on 17-under par after closing with a round of 69 at Castle Stuart Golf Links, in Inverness.
Mickelson was on 18-under par playing the last but, after rushing his five foot birdie attempt past the hole, he also missed his par putt coming back to sign for a round of 69 and set up a play-off.
"It's very special for me to have some success over here, in the Home of Golf. It's been the biggest challenges of my career, adapting to links style golf, and this was a great challenge for me this final round in some difficult conditions on firm ground. I played some good golf to come out on top, and this is really fulfilling and special," Mickelson said after the win.