The first set was shaky with Littler taking 13 darts in the second leg to get in, before pair exchanged breaks in leg three and four.
Littler, who beat four previous winners of the event on his way to winning it, held to claim the early advantage.
From there he clicked into gear, with Humphries, who had become just the third person to reach three successive Grand Prix finals, failing to create opportunities to snatch any initiative.
Littler took set two with a 64 checkout after a brilliant 177 set-up in leg five and he then got eight darts into a nine-darter in the opening leg of set three, before winning it after Humphries missed four darts at double.
Set four was won by Littler in another final-leg decider before Humphries got on the board by sensationally taking out 154 to pick up set five.
That could have been the spark for the 2023 winner but Littler was not willing to open the door and won the next two sets to seal the victory.
Humphries will walk away wondering what happened. He averaged 93.61 to Littler’s 92.15, while the 2024 world champion also hit more 100-plus scores and 180s.
Two years ago, Humphries won this event for his first major and Littler did not even have a tour card yet, but, remarkably, the pair have taken 15 of the past 21 major trophies between them.
