Keothavong began her 2009 season by launching her official website before heading to the ASB Classic where she reached the semifinals. En route, she defeated Mirjana Lučić, No. 8 seed Carla Suárez Navarro and Ayumi Morita before falling in a three-hour, three set battle to Elena Vesnina. This was only the second time in her career that she reached the semifinals of a WTA Tour event. Keothavong then competed in the Hobart International where she faced a tough draw in round one against world No. 25, Ágnes Szávay. Nevertheless, Keothavong came through without too much difficulty, beating Szávay in two sets. She lost to Virginie Razzano in the second round. Keothavong then headed to the main draw of the Australian Open for the first time in her career where she came up against Anna Chakvetadze, who was the 17th seed. She lost in a controversial match where a mistake by the umpire allowed Chakvetadze to serve first in the final set, an advantage which should have gone to Keothavong. Keothavong was the fourth seed in her next tournament, the Cellular South Cup, and she followed up on this seeding by reaching the semifinals of a WTA event for the second time in 2009. She defeated Maria Elena Camerin, Michelle Larcher de Brito and No. 5 seed Marina Erakovic on the way to being demolished by top seed Caroline Wozniacki in the semifinals. Despite this crushing defeat, a semifinal run was enough to help Keothavong make the hop from world No. 52 to world No. 48, her debut in the top 50. Keothavong then endured three consecutive first round defeats in the BNP Paribas Open, the Sony Ericsson Open (both Premier Mandatory tournaments) and a $100k ITF tournament in Tourhout, Belgium, where she was forced to retire due to a viral illness.