New head coach Luke Williams has been eager to add fresh faces to his squad in a bid to make a late push for the Championship playoffs.
With Yannick Bolasie having been released at the end of his short-term contract, Swansea have done business with Arsenal for the second time this season.
Charlie Patino is already spending a season-long loan in South Wales, the midfielder making 15 starts and nine substitute outings in all competitions.
Sagoe Jr has now been acquired by Swansea, the 19-year-old making the first senior loan switch of his career.
The prospect is given the chance to build on starring in Arsenal's youth ranks during 2023-24, chipping in with three goals and 10 assists from 16 appearances.
Four outings were made in the EFL Trophy earlier this season, providing him with experience against clubs in League One and League Two, but he will now make the step up to the Championship.
He could make his debut when Swansea play host to Plymouth Arygle in the Championship on Saturday afternoon.