The bar, which is located on the Southbank, was commended for "not just meeting the highest of standards, but surpassing them".
Dandelyan replaces the Savoy’s American Bar, which was knocked into second place.
Manhattan bar in Singapore took third place, and London’s Connaught Bar dropped to fifth place, being replaced by New Yorks NoMad. Bar Termini, which sat at ninth place last year, jumped three spots into sixth place.
The win follows Chetiyawardana's announcement earlier this week that he will close the four-year-old bar down and start a new project from scratch in its place. It is understood that this won’t happen until Spring next year.
New London entries include Matt Whiley’s Scout in 23rd place; and Swift in Soho at 46th.
Chris Moore’s east London bar Coupette, on Bethnal Green Road, took the prize for Best New Opening, making its debut on the list at eighteenth place.
Oriole in Smithfield market came just ahead at 17th place – the same ranking it achieved last year- while its big sister Nightjar dropped off the list this year.
The Gibson in Old Street, which was in 21st place last year, also disappeared from the list, while long-time list mainstay Happiness Forgets dropped to 35th place after sitting at 12th last year.
The Highest New Entry award went to The Old Man in Hong Kong's Soho, which made its list debut at an impressive tenth place.