Titterrell, an athletic front row who was selected for the 2005 Lions tour to New Zealand, missed just one match for Sale last season.
The 26-year-old has won four caps, making his Test debut against New Zealand in 2004, but was omitted from the elite player squad last year.
He has been competing with Sebastien Bruno for Sale's number two jersey and departs the injury-ravaged English champions for the Guinness Premiership's leaders.
Titterrell said: "Gloucester is a fantastic club - one of the strongest and most progressive in Europe - and I'm thrilled to be joining them.
"When I had the opportunity to speak to their coaching team I was hugely impressed with the standard of facilities, their vision for the club and their thirst for success.
"Sale were instrumental in my development as a rugby player and I thank them for that, but this is a new period in my career and I am excited about moving south."
Head coach Dean Ryan views Titterrell as another piece in the jigsaw as Gloucester build a team capable of competing with Europe's elite.
"We are attempting to develop our squad to a level that is capable of challenging anywhere in Europe," he said.
"To have the opportunity to sign a player of Andy's quality is great for us.
"He is an international-quality footballer and the opportunity to sign those sorts of players does not come around that often."