Jayawardene, 30, will turn out for the county from the end of April to mid-July before returning home for Sri Lanka's Test commitments, the website said.
"Signing such a world-class player and current international captain is a massive boost for the club ahead of the 2008 season," Derbyshire chairman Don Amott said.
"I can't wait to see Mahela -- as well as the likes of Rikki Clarke, Nayan Doshi, John Sadler and Wavell Hinds -- in action in a Derbyshire shirt and I am sure the members and supporters share my excitement."
Jayawardene, who leads Sri Lanka in a two-Test series in Australia next month, was voted the International Cricket Council's captain of the year in 2006.
The 88-Test veteran has scored 6,630 runs at an average of 49.84 with 18 centuries, including a best of 374 against South Africa in Colombo last year.
He has also played 261 one-day internationals with 7,232 runs and led Sri Lanka to the World Cup final in the Caribbean earlier this year.
Derbyshire's head of cricket John Morris said he was delighted that Jayawardene had signed.
"I knew that he was the right player after I had spoken to him and I could tell that he has the desire to play county cricket and contribute both experience and flair to Derbyshire's batting line-up," said Morris.