Walker, 18, impressed in nine outings for the Cobblers, but has now been recalled by the Blades as they bid to challenge for promotion to the Premier League.
Town boss Stuart Gray told the club's official website: "I think Kyle did very well with us and he was a credit to himself and his club.
"We thank Sheffield United for their help and we wish them and Kyle all the very best.
"I think Kyle enjoyed his time here and I am sure he will have benefited from the experience."