Plaisier's remarkable run sees him become just the fourth player to win a PDC ranking title without holding a PDC Tour Card.
The Dutchman, who came runner-up in back-to-back Players Championship events in July, survived six match darts from Rock in the final.
"I cannot believe it, to be honest, it's unbelievable," said Plaisier.
"Every game is tough but the final was a really hard game; I was hoping and praying I would get another chance.
"In the quarter-finals I managed to come back from 5-3 down against Jose [de Sousa] and I started thinking 'maybe this is my day'.
"I've been playing well all year and this is a crown on top of it."
A compelling final saw Rock land a 111 checkout to move half-way to victory at 4-3 up, before Plaisier won four of the next six legs to move to the brink of victory at 7-6.
Rock produced a skin-saving 112 checkout to force a decider, but spurned six match darts at doubles 16, eight and four, allowing Plaisier to wrap up victory on double top.
Plaisier began the day with wins over Matt Campbell, Ritchie Edhouse and Florian Hempel, before coming through deciding legs against Krzysztof Ratajski and De Sousa to reach the semi-finals, where he defeated fellow-Dutchman Danny Noppert 7-5.
Meanwhile, Rock produced some dazzling displays as he came agonisingly close to a third ranking title of the year, including a 110.89 average in his last 16 win over George Killington.
That game also saw Rock become the third player of the day to hit a nine-darter in Wigan, following Jamie Hughes and Callum Goffin's first round efforts against Niels Zonneveld and Jelle Klaasen respectively.
Players Championship 28 results
Last 16
- Jonny Clayton 6-5 Dave Chisnall
- Josh Rock 6-2 George Killington
- Dirk van Duijvenbode 6-1 Wessel Nijman
- Ryan Joyce 6-4 Mervyn King
- Wesley Plaisier 6-5 Krzysztof Ratajski
- Jose de Sousa 6-1 Mensur Suljovic
- Michael Smith 6-4 Ryan Searle
- Danny Noppert 6-5 Mickey Mansell
Quarter-Finals
- Josh Rock 6-4 Jonny Clayton
- Dirk van Duijvenbode 6-2 Ryan Joyce
- Wesley Plaisier 6-5 Jose de Sousa
- Danny Noppert 6-5 Michael Smith
Semi-Finals
- Josh Rock 7-6 Dirk van Duijvenbode
- Wesley Plaisier 7-5 Danny Noppert
Final
- Wesley Plaisier 8-7 Josh Rock
Nine-Darters
Jamie Hughes hit a nine-darter in his first round tie against Niels Zonneveld.
Callum Goffin hit a nine-darter in his first round tie against Jelle Klaasen.
Josh Rock hit a nine-darter in his fourth round tie against George Killington.
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