"It is with incredible joy that we can announce that our striker is back and will represent us for the next two seasons," the club wrote on Twitter.
Hallenius was a prestigious recruit when he was recruited to IFK Norrköping from Cypriot Apoel Nicosia.
But Hallenius got it tough and was goalless in the eight Allsvenskan matches he made.
The striker has previously made two appearances in Gif Sundsvall, most recently 2017–2019, and he is the club's most Allsvenskan goal scorer of all time with his 35 goals.
"It feels fantastic to come home, where both the heart and the head want to be," he says to the club's website.
Gif Sundsvall finished in sixth place in the Superettan last season.