The 21-year-old has struggled to make an impact at London Road this term, failing to make a single appearance for the high-flying League One outfit.
Ferdinand made 32 Championship outings for Posh last season, 15 of which starts, having arrived from Southend.
And Cobblers boss Aidy Boothroyd is happy to have brought him to Sixfields.
"Kane is a very attack-minded player who can play anywhere in midfield," said Boothroyd.
"He's someone we've been watching for a while and he will bring more energy to the midfield.
"I know the priority is to bring in another centre-forward but if you can't get the one you want and you have got to wait a little bit of time to get the one you want, then you have got to add goals in other ways.
"If we can bring another centre-forward in next week then we will try and do that, Jacob Blyth is back training again now with Leicester and we just want to make sure that he is fully fit before doing anything."
Ferdinand is able to feature in Northampton's FA Cup first-round tie against non-league Bishop's Stortford next week.