The projected figure of 18.7 million global visitors in 2014 is 300,000 more visitors than the 2013 top destination city Bangkok, says the report Mastercard Global Cities Index.
Bangkok was the second most popular city with 16.4 million visitors predicted for 2014 while Paris was placed third.
London mayor Boris Johnson said: "With nearly nineteen million visitors this year London is the world's favourite place to visit.
"Our city perfectly combines history, heritage, arts and culture, not to mention vast amounts of green space and major events that are the envy of the planet."
Now in its fourth year, the index provides a ranking of the 132 most travelled cities around the world.
Europe boasts two of the top five cities, London and Paris, with Bangkok, Singapore, and Dubai making up the global top five.
Overall, Europe boasts eight of the top 20 destination cities by international overnight visitors.
Istanbul (7th), Barcelona (11th), Amsterdam (12th), Milan (13th), Rome (14th) and Vienna (17th) all make the cut.
In 2013, according to the Office of National Statistics International Passenger Survey, London hosted over 16 million international visitors in an year for the first time.
Tourists from around the world flocked to London to attend exhibitions, visit royal palaces, dine at Michelin starred restaurants, and watch world-class sporting events.
"The recognition of this year's top international destinations reinforces the continued importance of cities as business, cultural and economic hubs," Ann Cairns, President of International Markets, Mastercard said.
London being recognised as the top destination will boost its ability to continue to be a global leader, whether hosting events to draw in further investment, or inspiring those within to drive growth, Cairns said.
Some of the major cultural events in London this year drawing millions of international visitors include, 'Ming: 50 Years that changed China' at the British Museum, 'Constable: The Making of a Master' at the V&A and 'Rembrandt: The Final Years' at the National Gallery.
Among other 2014 events likely to draw global attention is the commemoration of the 100th Anniversary of World War I with the re-opening of the Imperial War Museum this month and the Great War in Portraits exhibition.
An exhibition about fictional detective Sherlock Holmes and the Thames River Festival in September offers a feast of activities for visitors.