This was mainly because of a sharp downturn in Indian visitors, who come both for tourism as well as business.
Arrivals from India in May 2009 fell 41 percent to 5,697 from the same month last year.
May is usually considered part of the off-season in the island, where arrivals peak during the winter in the northern hemisphere.
But this year, Sri Lanka also suffered from bad publicity generated by fierce fighting between government forces and Tamil Tigers, whose remnants and top leadership were wiped out in the final phase of a military campaign in mid-May.
The fighting generated news reports of civilian casualties and also led to calls from Western powers like the UK, a traditional source of visitors to the island, for probes into allegations of human rights abuses.
Arrivals from Western Europe in May 2009 fell 15.3 percent to 8,