Lewis was facing Beaton - who was on his 20th consecutive World Matchplay appearance and it was a game he could have won more comfortably.
He went 8-6 up but 'The Bronzed Adonis' levelled and it went all the way, in the end it finished 11-9 in a tie-break to 'Jackpot' who averaged 97, hit six 180's and 57% on the doubles.
The pair were even to begin with the match tied at 4-4 but Lewis approached the break with more to smile about after opening up a two-leg advantage at 6-4 up playing some quality darts - averaging 103 with five 180's and 75% on the doubles.
Despite that though, Beaton returned to break after four missed darts at double from Lewis and this saw him trail 6-5. From there, Lewis looked to regain the upperhand breaking back himself but Beaton kept at 7-6 behind as both struggled to hold.
'Jackpot' led 8-6 and let out a roar after a 91 checkout but Beaton wasn't done yet. He broke after Lewis missed two more at double and produced a stunning 111 checkout to level proceedings at 8-8.
Lewis went one away at 9-8 though but Beaton forced overtime. The two-time World Champion responded hitting his sixth 180 and a 104 checkout to go one away once more at 10-9 up.
He left himself on 72 with Beaton left on 115 after not pressuring and T16, D12 was hit for a brilliant win for Lewis.
Click here for more information about the World Matchplay, including the tournament bracket, TV coverage and prize money breakdown.
Dave Chisnall (94.2) 6-10 (99.35) Vincent van der Voort
Ian White (93.44) 12-13 (90.41) Joe Cullen
Daryl Gurney (92.37) 10-5 (90.29) Ricky Evans
Gerwyn Price (90.73) 7-10 (90.92) Danny Noppert
Adrian Lewis (97.27) 11-9 (89.94) Steve Beaton
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