Evert, 60, is one of the most decorated women in the history of tennis, winning 18 Grand Slam singles titles. In singles, she reached the semi-finals or better in the 34 Grand Slams she entered from the 1971 US Open through the 1983 French Open, and in 52 of the 56 she played in her career.
"I am so excited to return to Singapore as an Official Ambassador of the BNP Paribas WTA Finals Singapore presented by SC Global," Evert said.
"I was blown away last year by the enthusiasm and support of all the fans. The bar has been set high, but I am looking forward to an even bigger and better event this year."
The event will be hosted in Singapore through 2018.
Stacey Allaster, Chairman and CEO of the WTA, said: "Each and every match of the BNP Paribas WTA Finals Singapore presented by SC Global is like a Grand Slam final, as evidenced by the fact that the WTA Finals was the most-watched tournament of 2014.
"Once again, we look forward to bringing together the past, present and future for a celebration of the world’s best tennis players who have the power to inspire many generations to come."
Singapore (2014-18) is the ninth city to host the WTA Finals, joining Boca Raton (1972-73), Los Angeles (1974-76, 2002-05), Oakland (1978), New York City (1977, 1979-2000), Munich (2001), Madrid (2006-07), Doha (2008-10) and Istanbul (2011-13).