The club have described the agreement as "an improved deal" for the versatile 21-year-old, who joined from Leeds in July 2009 during Martin O'Neill's time in charge.
"I am absolutely delighted," Delph told avfc.co.uk. "The club has shown great commitment in me by offering me this deal and I was more than happy to sign it."
Delph added: "I am happy and my family are happy - so everyone is happy. I want to push on now, improve and play a part as we look to finish the season on a high and build for next season.
"I am really pleased to have extended my association with the club."
Villa boss Gerard Houllier hailed Delph's attitude.
"I know Fabian hasn't played a lot for us because he has just got over his long-term injury but we are very confident he will become a very good player for Aston Villa," he said.
"The fact he signed the contract means he trusts us too. I think he's a good footballer, he will get stronger and stronger and he will improve his game.
"When you sign a player - or re-sign a player - you need to make sure he has the right attitude for the club and the fans and Fabian certainly fits that bill."
England Under-21 international Delph has suffered a largely frustrating season after an anterior cruciate ligament injury suffered at the end of the 2009-10 campaign.
Source: PA
Source: PA