The waiving of the fee – usually $35 for tourists – will run for six months from 1 August and covers 45 countries – six more than originally planned when the scheme was going to launch in May.
The scheme was suspended following the Easter Sunday bombings, which killed more than 250 people.
A media briefing on the official implementation will take place in Colombo on Wednesday.
Luxury tour operator Abercrombie & Kent welcomed the news.
Kerry Golds, managing director, said: “Sri Lankans need tourism for their economy, and we can help them – the news that they have lifted their visa fees for UK citizens will undoubtedly draw Brits to this jewel of an island.
“We’ve seen an uplift in enquiries, but still slight caution from our clients. Our message is ‘go now, before everyone else does’.”
