"Honestly, I am made up with the win. I am just so happy," said Smith, who suffered first-round exits in New Zealand and Australia in his only two other appearances in the 2026 World Series.
"You are playing Gerwyn Price - one of the best players in the world. You have got to up your game."
Smith beat Northern Ireland's Josh Rock 10-7 in the last eight and Dutch hope Gian van Veen 11-8 in the semi-finals to give himself a shot at the £100,000 winner's prize.
Price, meanwhile, made it past England's James Wade in the quarter-finals before beating compatriot Jonny Clayton - Littler's conqueror - in the last four.
The 2020 and 2022 winner won back-to-back legs to make it 5-5 against Smith in the final but was hanging on as his opponent continued to score heavily albeit with a lower checkout success.
Smith, however, was far more clinical after the interval, winning the next three legs, including back-to-back checkouts of 127 and 123.
The checkouts cooled but Smith won a succession of scrappy legs to seal victory as Price's game deserted him.
Earlier, Littler's bid for a clean sweep of all major PDC titles in 2026 was ended by a 10-4 defeat by Clayton in the quarter-finals.
The world number one had followed his World Championship triumph at Alexandra Palace in January by winning titles at the World Masters, UK Open, Premier League, World Cup of Darts and World Matchplay.
But after threatening to boycott events in the Netherlands after being roundly booed by the crowd during his last-16 win over Nathan Aspinall, the Warrington-based player failed to produce his best darts against Clayton.