The 32-year-old has been away with the Rajasthan Royals at the Indian Premier League and, after sitting out the Lightning’s next three games, will be in line to play in their final 10 fixtures.
Buttler, who starred as Lancashire won the Blast title in 2015, would also be available for the knockout stages if Glen Chapple’s side qualify for the quarter-finals.
“I’m really looking forward to pulling on the Red Rose once again and representing Lancashire Lightning in this summer’s Vitality Blast,” Buttler said.
“To have the opportunity to play so many matches in this year’s Blast is really exciting for me and it’s a chance to really help the team after coming so close in last year’s final.
“It’s always a great feeling to come back and play at Emirates Old Trafford in front of our members and supporters and it will be great to see some familiar faces in a couple of weeks’ time.”
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