Whittaker, who was described by Hibs manager Neil Lennon as ‘three players in one’ earlier this week, won’t be eligible to play in today’s Betfred Cup match against Montrose.
Lennon added: “I think it would be a real coup for this club. We’ll be getting three players in one with Steven.
“He can play in both full back positions, he is excellent in midfield and has had a stellar career – and I believe there is plenty more to come.”
Whittaker, capped 31 times for Scotland, spent seven years at Hibs and helped the Easter Road side to win the Scottish League Cup in 2007 before joining Rangers in a £2 million move in August of that year.
He made more than 200 appearances for the Ibrox side in all competitions, scoring 28 goals, and left to join Norwich City in June 2012.
The Edinburgh-born defender played more than 100 games for the Canaries, netting seven goals, with the Carrow Road side confirming that the Scot would be released at the end of his contract.
Whittaker told Hibernian’s website: “I am delighted to be back at Hibernian. When I decided to return to Scotland, Hibernian was the club I hoped to come to.
“While the discussions have taken a while, they have always been positive and I am very pleased to be back playing at Easter Road for the Hibernian fans, and I hope I can play my part in ensuring a successful return to the top flight.”