Jayawardene, 39, has played in T20 leagues around the world since retiring from international cricket in 2015 and has previously turned out in England for Sussex and Somerset.
"I'm very excited about joining Lancashire Lightning for the NatWest T20 Blast this summer," Jayawardene said in a Lancashire press release.
"Lancashire is a huge county with a fine history in the game. There is a young group of players at the club and I'm really looking forward to the opportunity to working with them."
Jayawardene has played in 149 Tests, scoring nearly 12,000 runs at an average of just below 50, and has amassed over 14,000 runs in white-ball cricket.
He will join up with Lancashire in July.
"Mahela is a truly world-class batsman who scores runs all around the wicket," said Lancashire head coach Glen Chapple.
"It will be a fantastic opportunity for our young players to learn off him and for our fans to watch one of the game's greats."
First Published: May 8, 2017, 8:13 PM IST