The 20-year-old playmaker has been a key part of the B Team again this season, racking up 10 appearances in the PL 2 whilst captaining the side in all three of the EFL Trophy group stage fixtures.
He currently captains Nottingham Forest's under 21 side and last year he signed a new two-year contract, keeping him at the City Ground until June 2026.
Northampton manager Kevin Nolan opened up on Perry and admitted that he thinks he will play a major role at the club during the second half of the season.
"Ben is a player I know a lot about," said manager Kevin Nolan.
"Andy Reid at Nottingham Forest rates him very highly, not just as a player but as a person too, and we have watched him a number of times and have always been impressed.
"He is someone who we think can come in and have an impact on our squad.
"We are pleased to have him in the building, and we hope this can be the start of an excellent relationship between ourselves and Forest.
"Ben will help us and be with us for the rest of the season, and he will be a better player for his time with us.
"We have been really pleased with our work this month and the arrival of Ben completes that."