The England Under-21 defender arrived at Villa's training ground at Bodymoor Heath on Thursday morning before undergoing a medical and completing the formalities of his move.
He will be available to face his former club, Sheffield United, in Saturday's FA Cup clash at Bramall Lane.
Walker said: "I'm excited about being here and proving that I'm good enough to play in the Premier League.
"That's why Tottenham bought me from Sheffield United and that's what I'm keen to show here at Villa.
"This is a great opportunity for me and I'm looking forward to taking it.
"I know several of the players here from England Under-19s and England Under-21s - Nathan Delfouneso, Ciaran Clark and Marc Albrighton.
"I'm sure those lads will help me to settle in and enjoy my time at Villa. I'm really keen to contribute and compete and prove myself here."
Villa manager Gerard Houllier said: "We're pleased that Kyle will be with us until the end of the season.
"He is 20 years old, an attacking full-back and a very promising young player. He will be a valuable addition to our defence."
Source: PA
Source: PA