The first European final in men's or women's football to feature two Swedish clubs saw the teams welcomed onto the 3Arena pitch by vocal home support, but that did not seem to settle Hammarby nerves, as captain Alice Carlsson gave goalkeeper Melina Loeck an awkward backpass in the third minute, which the German just about managed to clear.
As expected, Felicia Schroder was the focal point of the Hacken attack, and she had the first chance of the game, taking the ball down well but shooting wide as Loeck closed her down.
But soon it was the visiting defence that was coming under pressure - only a key block prevented a Sofia Reidy volley finding the net at a corner, then after Stine Sandbech was booked 15 minuntes in for a poor challenge just outside the area, Vilma Koivisto curled a low free-kick just past the post.
Sweden winger Monica Jusu Bah started to have some joy down the Hacken left, robbing Carlsson of possession before trying to catch Loeck off her line with an effort from distance, but the scrambling goalkeeper blocked it with her legs. But midway through the first half, Jusu Bah getting free again proved costly for the hosts.
Carlsson's difficult afternoon continued when she committed herself to a through ball, but failure to cut it out gave Jusu Bah all the time in the world to square the ball across the box to Schroder, who coolly placed her fifth goal of the competition past Loeck.
Schroder should have had her sixth mere minutes later when she got in behind the defence on the right, but despite having a shooting angle, she attempted to return the favour and square to Jusu Bah, but this time Carlsson made amends, doing enough to put the winger off, who shot wide.
That seemed to be the final straw for Bajen's defence, who managed to deal with everything else that came their way before half-time. At the other end, the hosts didn't do enough to equalise - Reidy stretched Fanney Birkisdottir with a curling effort, before the Icelandic goalkeeper dealt with a tame shot from Svea Rehnberg and saw a Fanny Peterson header go wide before the break.
Head coach William Stromberg kept faith with his starting XI for the beginning of the second half, which began with his side on top, though a Koivisto hit from distance which flew wide three minutes in was their only notable chance.
Four minutes later, Anna Anvegard came very close to showing Koivisto exactly how its done - she took aim from the edge of the area, only for her effort to cannon off the post, before Schroder put her follow-up wide.
Just before the hour mark, Hammarby threw on Vilde Hasund, who immediately added more creativity to the home attack, but the end product was still lacking, as Koivisto and Elin Sorum both ballooned efforts high and wide, while a Stina Lennartsson cross struck the upright and bounced clear.
But Elena Sadiku's side, who saw off well-fancied Eintracht Frankfurt in the semi-finals, controlled the tempo as the match entered its final 10 minutes, limiting the hosts to a Lennartsson header that missed the target. Hammarby then put together one of the best attacks of the game in the 87th minute, however, Emilie Joramo couldn't provide the finish it merited.
Hacken, who beat Hammarby to first place in the 2025 Allsvenskan Women, closed out a 1-0 victory - their fifth head-to-head win in the last six meetings - that they will take back to Gothenburg ahead of the return leg on Friday 1st May.
Not counting the second-leg defeat to Sporting Club in the quarter-finals which they won on penalties, it's a first defeat for Hammarby since they lost to Hacken in the league in October. They must now inflict just a second loss on Getingarna since September if they are to turn the tie around.