Just one point from their previous three matches, coupled with Hammarby's win at Malmo two days earlier, had seen Sirius knocked off the top of the standings for the first time since the second week of the season, albeit only on goal difference.
One point would be enough to reclaim first place, but Sirius put themselves on course for all three with a quarter of the match played. Isak Bjerkebo dug out a cross from the left side of the area, which struck the arm of the committed Tom Trybull.
Bjerkebo took the penalty responsibility himself, and though Tim Ronning went the right way, he was unable to reach the spot-kick which nestled in the bottom corner.
Then the Uppsala side dealt a blow to their visitors by doubling their lead with seconds to play in the first half, as Bjerkebo ran onto a through ball down the wing and played a perfectly-weighted square ball to Joakim Persson, who applied the simple finish.
Early in the second half, Malte Persson wasted a big chance to get the visitors back into the contest, but besides that, it was a quiet second 45 minutes which featured just one effort on goal per side, meaning Sirius had comfortably held on for their first win since 10th October, while back-to-back losses keep Halmstad six points from guaranteed safety.
Hammarby will have the chance to go return to the top of the table on 6th November when they face Elfsborg, before Sirius take on Kalmar two days later.
Follow the Allsvenskan title race and relegation battle on Flashscore.