Smith defeated fellow Englishman Nathan Aspinall 16-5 in the final in Wolverhampton on Sunday night.
Before, "Bully Boy" had lost eight major finals. The 32-year-old won the Eric Bristow Trophy and prize money of £150,000.
Smith, among others runner-up at the World Championships 2019 and 2022, at the World Matchplay 2019 and at this year's European Championship, had earlier eliminated Dutch veteran Raymond van Barneveld 16-12 in the semi-finals.
Meanwhile, two-time World Championship semi-finalist Aspinall beat Luke Humphries by the same scoreline.
In a one-sided final, Smith managed seven breaks against his overstrained opponent Aspinall.
Smith, the "eternal runner-up" from St Helens, ended his final trauma with a dominant performance at the Aldersley Leisure Village.