Statistics Mauritius said arrivals in April fell 3.7 percent year-on-year to 76,223 due largely to declining numbers from Europe, Mauritius' main source market for its tourism sector.
Amid a lingering debt crisis and stagnant economic growth, Europeans have cut down on long-haul holidays to sun-drenched destinations like the Indian Ocean.
Hotels have also been forced to discount heavily in a fight for market share in a country where tourism makes up around 10 percent of the economy.
The Port Louis government expects tourist numbers to hit the one million mark this year after remaining stuck around the 965,000 level in 2012. But some economists say that figure may be optimistic.
"We will have to revise our expectations for the tourism sector as the deepening of the crisis in our main markets will force people to cut spending," Chandan Jankee, economic professor at the University of Mauritius told Reuters.
Wary of its reliance on Europe, Mauritius and regional rivals like the Seychelles islands are increasingly looking to new markets in Asia to drive growth in tourism.