Defeat to FC Copenhagen was Inter Turku's only loss in their previous 10 outings in all competitions, a more intimidating run of form that that of HJK, who arrived to the final in Tampere having lost three of their previous seven.
The wait to see who would lift the cup went on longer than expected, as kick-off was delayed by 10 minutes, and then the game was only several minutes old when it was halted for 40 minutes owing to two separate medical emergencies in the crowd.
And it was during the extended period of added time that Inter Turku broke the deadlock, as Herman Sjogrell produced an in-swinging cross into the box, which Alie Conteh controlled on his chest before using his head to nod the ball past Matej Markovic.
After the break, Teemu Pukki had chances to score in the Finnish Cup final for a second year in a row, and Mouhamed Gueye also went close, but HJK only created one shot on target throughout the 90 minutes, and in the end, FC Inter held on comfortably to win the cup.
It's a third Suomen Cup title for Inter Turku, and ensures them of at least UEFA Conference League football for next year. The Helsinki side must now aim for a place in Europe via the league after failing to add to their 15 cup successes.