The Geneva-based body, which is backed by governments and private donors such as Microsoft founder Bill Gates, said South Korea was to double its contribution over the next three years.
The ministry of health is to contribute $6 million to the Global Fund for 2014-2016, and the foreign ministry is to pay $10 million in five annual instalments from 2013-2017, drawn from a levy on all passengers leaving South Korea on international flights.
South Korea's 1,000 won ($0.95) levy, known as the "Global Poverty Eradication Tax", was introduced in 2007, primarily to contribute financial resources to fight poverty and disease in impoverished countries.
"The Republic of Korea is a trend-setter in the use of innovative funding methods to help fight the three diseases," said Mark Dybul, head of the Global Fund, in a statement.
"In doubling its contribution, Korea is also leading the way for other G20 countries to follow," he added.
South Korea has contributed $19 million since it started supporting the Global Fund in 2004, of which $6 million was pledged for 2011-2013.
The idea of imposing such a levy first came from French organisation Unitaid, which said it has collected $1.06 billion at the end of 2011.
The Global Fund focuses on developing nations, including South Korea's hermetic neighbour North Korea.
Global Fund grants to North Korea totalling $67 million have since 2010 funded the diagnosis and treatment of 120,000 cases of tuberculosis and the distribution of 710,000 mosquito nets to ward off malaria.