The allrounder, bound for Sussex on a three-year deal at the end of the season, moves to Taunton for their 50-over campaign having spent part of the campaign at Gloucestershire
Lancashire's Danny Lamb is braced to play for his third county of the season after agreeing to a Metro Bank One-Day Cup loan stint with Somerset.
The 27-year-old, who recently signed a three-year contract with Sussex, will arrive at Taunton for the group stage of the competition.
Four-time winners Somerset begin their campaign against Warwickshire on Friday (August 4).
Lamb has claimed 28 wickets in 18 List A matches at an average of 29.92 while also excelling with the bat, hitting nearly 300 runs at an average of 41.71.
He spent a short period with Gloucestershire earlier in the campaign, playing four T20 Blast matches and a single County Championship game.
Lamb was part of Lancashire's run to both domestic white-ball finals last summer (Alex Davidson/Getty Images)
"I'm looking forward to this new opportunity and to contributing to the team both on and off the field," said Lamb. "I've seen how much white-ball cricket is valued in Taunton and I'm looking forward to experiencing that as part of the home team."
Paul Tweddle, Somerset coach during the One-Day Cup, added: "It's important to have a good blend of players who have experience within the format alongside the younger players in the squad.
"Danny helps us to provide that balance. He's got a good record in 50-over cricket and helped Lancashire to the final last year.
"After Ben Green's selection in The Hundred and recent injuries, Danny's signing adds depth and quality to us as a team."
Welcome to www.thecricketer.com - the online home of the world’s oldest cricket magazine. Breaking news, interviews, opinion and cricket goodness from every corner of our beautiful sport, from village green to national arena.