The club has never won the 20-over tournament which began in 2003 and only twice reached Finals Day.
Bess, who played four County Championship matches for Yorkshire earlier this summer on loan from leaders Somerset, has been brought back for the first 10 games of the 14-match group stage.
Yorkshire have already signed highly-rated West Indies batsman/wicketkeeper Nicholas Pooran for the first five games of the T20, with the club’s first match taking place against Nottinghamshire at Emerald Headingley tomorrow week.
Bess’s deal runs until the resumption of Championship cricket when he will return to help Somerset’s quest for their maiden title.
The 21-year-old off-spinner, who played two Tests for England last year before losing his spot, could line up against Yorkshire when the leaders visit Headingley for a Championship game starting on Saturday.
Yorkshire would ideally like to sign Bess permanently but he has a year left on his contract at Taunton where he is second-choice spinner to Jack Leach.
Leach misses the Championship fixture at Headingley along with all-rounder Lewis Gregory as they are part of the England Lions squad for a four-day match against Australia A starting at Canterbury on Sunday.
Bess, who took seven wickets and scored a half-century in Somerset’s latest Championship win over Nottinghamshire this week, has played only two T20 games.
“I’ve played a bit in red ball now but haven’t really established myself as a T20 cricketer,” he said. “I think it’s a great opportunity for me to really put the skills I’ve practiced into performances.
“I had some great fun when I was with the lads previously, and I managed to forge a lot of good relationships. It will be nice and easy to get back into that environment again and get stuck into a great tournament.”
Bess impressed on Championship duty for Yorkshire, scoring 156 runs and taking seven wickets. He bowled on some unhelpful pitches in rain-affected matches so could be happy overall with his contribution.
As to his long-term future, he said: “I’ve gone back and done well for Somerset and I’ve got a year left there. I’ve got to see how things go.
“A lot of things can happen within a year, as I know; probably the greatest example I can give is that I got to the top of Mount Everest with the Test stuff and then fell off.
“I just want to play my 10 games for Yorkshire, contribute and push hard and then see what happens.”
Martyn Moxon, Yorkshire’s director of cricket, said that Bess’s signing – hot on the heels of Pooran’s capture – proved Yorkshire’s commitment to winning the T20.
The tournament likely represents their last chance of silverware this year, with this week’s eight-wicket defeat to Essex at Chelmsford leaving them an uphill task to overhaul both second-placed Essex and Somerset in the Championship.
“We want to have a really good go at the T20 and I think we’ve shown that in signing Nicholas Pooran for the first five games,” said Moxon. “He’ll hopefully help get us off to a good start and, with Dom, we’ve seen just what a good cricketer he is in the four Championship games he spent with us.
“In a way, it’s tough on our back-up spinners, but, at the same time, when someone of Dom’s ability and quality becomes available, then if we’re serious about trying to win the competition, then we’ve got to look at it.
“I think we go into the T20 campaign with a very strong squad.”