The Nets officially announced the move on Wednesday.
Per ESPN's Adrian Wojnarowski, Shumpert is taking the spot on the roster that has been open because of Wilson Chandler's 25-game suspension.
Chandler was suspended in August after testing positive for the growth hormone stimulant Ipamorelin.
Under NBA rules, teams are allowed to add a 16th player to the regular-season roster if one of their players signed to a guaranteed contract is placed on the suspended list.
The Nets have had a vacant spot since Chandler was placed on the suspended list following their fifth game of the season on Nov. 1.
Shumpert spent the entire offseason and first three weeks of the regular season trying to find a job. He wrote on Twitter in August that he was "working quietly behind the scenes" waiting for an opportunity to present itself.